user: You are a structured reasoning expert tasked with solving problems step by step. 
You first think about the reasoning process in the mind and then provide the answer. The reasoning process and answer should be enclosed within <think> </think> and <answer> </answer> tags, respectively, i.e., <think> reasoning process here </think> <answer> answer here </answer>. 
Given a question and the associated knowledge graph triplets (entity, relation, entity), you are asked to answer the question with these triplets and your own knowledge. 
You can break down the original question into several sub-questions and explore the given knowledge graph to solve them step-by-step. If there are multiple possible answers, choose one as the final answer. 
After thinking, when you finally reach a conclusion, clearly state the answer within <answer> </answer> tags, i.e., <answer> answer here </answer>. 
Question: What is the source of the body of water under the Old London Bridge? 
Knowledge Triplets: River Thames, location.location.partially_containedby, Kent
United Kingdom, location.location.containedby, Europe
River Thames, location.location.people_born_here, Jimmy Clarken
Old London Bridge (1616) by Claes Van Visscher, common.image.size, m.029rgks
River Thames, location.location.events, Rowing at the 1908 Summer Olympics – Men's coxless four
River Thames, location.location.adjoin_s, m.049x40b
Structure, freebase.type_hints.included_types, Location
River Thames, location.location.events, The Boat Race 2012
Body Of Water Spanned, rdf-schema#domain, Bridge
Brentford Ait, location.location.containedby, United Kingdom
Thames Tunnel, common.topic.notable_types, Structure
m.049x3_k, location.adjoining_relationship.adjoins, River Thames
Bridge, freebase.type_profile.strict_included_types, Structure
Architect, freebase.type_profile.strict_included_types, Topic
Peter Colechurch, architecture.architect.structures_designed, Old London Bridge
River Thames, location.location.people_born_here, Frithuswith
Maidenhead, travel.travel_destination.tourist_attractions, River Thames
River Thames, location.location.events, Caesar's invasions of Britain
River Thames, common.topic.webpage, m.09xltpj
Bridge, freebase.type_profile.published, Published
m.02_56pg, location.adjoining_relationship.adjoins, River Thames
London, location.location.partiallycontains, m.0wg9mlk
Bridge House Estates, architecture.architectural_structure_owner.structures_owned, m.0g4wm79
Location, freebase.type_hints.included_types, Topic
River Thames, geography.body_of_water.islands, Canvey Island
Lower Thames Crossing, common.topic.notable_types, Location
Bridge, type.type.properties, Locale
Nathaniel Dance-Holland, people.person.parents, George Dance the Elder
Douglas Osborne, people.person.place_of_birth, River Thames
Nathaniel Dance-Holland, people.person.gender, Male
Europe, location.location.contains_major_portion_of, France
The Boat Race 2012, time.event.locations, River Thames
River Thames, location.location.events, Rowing at the 1908 Summer Olympics – Men's eight
Architect, people.profession.corresponding_type, Architect
m.0g4wm79, architecture.ownership.owner, Bridge House Estates
Marchioness disaster, time.event.locations, River Thames
m.0wg9n1x, location.partial_containment_relationship.partially_contains, River Thames
Chiswick Eyot, location.location.containedby, United Kingdom
Isleworth Ait, geography.island.body_of_water, River Thames
Chronicles of London bridge, book.written_work.subjects, Old London Bridge
River, freebase.type_profile.kind, Definition
m.0wg9mlk, location.partial_containment_relationship.partially_contains, River Thames
Old London Bridge, transportation.bridge.body_of_water_spanned, River Thames
River Thames, travel.travel_destination.tour_operators, Adventures by Disney - England and France Vacation
Rowing at the 1908 Summer Olympics – Men's coxless four, time.event.locations, River Thames
Bridge, common.topic.article, m.03bqfkm
River Thames, location.location.people_born_here, Rhona Haszard
m.0g4wm79, architecture.ownership.structure, Old London Bridge
River, freebase.equivalent_topic.equivalent_type, River
Oliver's Island, geography.island.body_of_water, River Thames
River Thames, location.location.adjoin_s, m.049x40w
Richmond, London, location.location.containedby, London
River Thames, location.location.adjoin_s, m.0j8lh46
Chronicles of London bridge, common.topic.notable_for, g.12586g391
River Thames, location.location.adjoin_s, m.04nrby2
London, location.administrative_division.country, United Kingdom
Mansion House, London, architecture.structure.architect, George Dance the Younger
London, base.biblioness.bibs_topic.subsumes, London
Isembert de Saintes, common.topic.notable_for, g.125fs18l3
Body Of Water Spanned, type.property.master_property, Bridges
River Thames, travel.tourist_attraction.near_travel_destination, Richmond, London
Architect, freebase.type_profile.equivalent_topic, Architect
Old London Bridge, common.topic.notable_types, Bridge
m.0j8lh46, location.adjoining_relationship.adjoins, River Thames
United Kingdom, location.country.capital, London
Locale, rdf-schema#range, Location
Mansion House, London, location.location.containedby, United Kingdom
River Thames, geography.river.basin_countries, England
Nathaniel Dance-Holland, people.person.nationality, England
Kent, location.location.containedby, United Kingdom
Thames Tunnel, base.undergroundhumanthings.underground_object.underneath, River Thames
Kent, location.location.containedby, England
Above the Below, time.event.locations, River Thames
Old London Bridge, architecture.structure.architect, Peter Colechurch
George Dance the Elder, people.person.children, James Dance
Monk, people.profession.people_with_this_profession, Isembert de Saintes
United Kingdom, location.country.first_level_divisions, England
London, travel.travel_destination.tour_operators, Adventures by Disney - England and France Vacation
Richmond, London, location.location.containedby, United Kingdom
Bridge, freebase.type_profile.strict_included_types, Topic
m.049x40b, location.adjoining_relationship.adjoins, River Thames
Old London Bridge, architecture.structure.architect, George Dance the Elder
James Dance, people.person.parents, George Dance the Elder
m.02shnt5, location.adjoining_relationship.adjoins, River Thames
Bridge, type.type.properties, Clearance Below
m.049x3tw, location.adjoining_relationship.adjoins, River Thames
Rowing at the 1908 Summer Olympics – Men's eight, time.event.locations, River Thames
Old London Bridge, architecture.structure.destroyed_by, Demolition
Structure, freebase.type_hints.included_types, Topic
Kent, base.biblioness.bibs_location.country, England
England, location.administrative_division.country, United Kingdom
Chronicles of London bridge, common.topic.notable_types, Book
m.0wg9mlk, location.partial_containment_relationship.partially_contained_by, London
Three Men in a Boat, common.topic.notable_types, Book
Isembert de Saintes, projects.project_participant.projects, m.0j9tfpt
Two Tree Island, geography.island.body_of_water, River Thames
River Thames, location.location.adjoin_s, m.049x3_9
Old London Bridge, architecture.structure.owner, m.0g4wm79
Bridge, type.type.expected_by, Bridges of this type
River Thames, base.undergroundhumanthings.location_on_top_of_something_buried.underground_object, Greenwich foot tunnel
Kent, location.administrative_division.country, United Kingdom
Peter Colechurch, people.person.profession, Monk
Clearance Below, rdf-schema#domain, Bridge
Nathaniel Dance-Holland, people.person.place_of_birth, London
Bridge Type, type.property.schema, Bridge
Great Synagogue of London, location.location.containedby, United Kingdom
Frog Island, London, geography.island.body_of_water, River Thames
m.049x3_9, location.adjoining_relationship.adjoins, River Thames
Bridge Type, owl#inverseOf, Bridges of this type
Bridge, freebase.type_profile.equivalent_topic, Bridge
Demolition, base.architecture2.destruction_method2.structures_destroyed_this_way, Arlington Apartments demolition
Book, freebase.type_hints.included_types, Topic
England, base.aareas.schema.administrative_area.administrative_parent, United Kingdom
River Thames, base.ontologies.ontology_instance.equivalent_instances, m.09klvvm
River Thames, location.location.partially_containedby, London
Old London Bridge, common.topic.image, Old London Bridge (1616) by Claes Van Visscher
Isembert de Saintes, architecture.architect.structures_designed, Old London Bridge
James Dance, people.person.nationality, England
Bridge Type, type.property.reverse_property, Bridges of this type
George Dance the Elder, architecture.architect.structures_designed, St Botolph-without-Bishopsgate
m.049x40q, location.adjoining_relationship.adjoins, River Thames
St Botolph's Aldgate, location.location.containedby, United Kingdom
Topic, freebase.type_profile.published, Published
River Thames, location.location.events, Rowing at the 1908 Summer Olympics – Men's single sculls
Bridges, type.property.expected_type, Bridge
River Thames, location.location.adjoin_s, m.02shnt5
Old London Bridge, common.topic.notable_for, g.1258wmx7n
St Botolph's Aldgate, architecture.structure.architect, George Dance the Elder
Caesar's invasions of Britain, time.event.locations, Kent
River Thames, location.location.partially_contained_by, m.0wg9mlk
Peter Colechurch, base.architecture2.architectural_designer.structures_designed, Old London Bridge
m.0j9tfpt, projects.project_participation.participant, Isembert de Saintes
Richmond, London, location.location.containedby, England
River Thames, location.location.adjoin_s, m.049x40h
George Dance the Elder, people.person.gender, Male
Reading, location.location.containedby, United Kingdom
River Thames, travel.tourist_attraction.near_travel_destination, Henley-on-Thames
Woolwich foot tunnel, base.undergroundhumanthings.underground_object.underneath, River Thames
Greenwich foot tunnel, common.topic.notable_types, Structure
River Thames, geography.body_of_water.islands, Chiswick Eyot
River Thames, location.location.adjoin_s, m.049x400
River Thames, location.location.events, Rowing at the 1908 Summer Olympics – Men's coxless pair
m.049x40h, location.adjoining_relationship.adjoins, River Thames
Canvey Island, geography.island.body_of_water, River Thames
Architect, freebase.equivalent_topic.equivalent_type, Architect
Old London Bridge, base.architecture2.structure2.lead_designer, Peter Colechurch
Isle of Sheppey, common.topic.notable_types, Location
Kent, location.administrative_division.second_level_division_of, England
Old London Bridge, transportation.bridge.body_of_water_spanned, River Thames
Clearance Below, type.property.schema, Bridge
Rowing at the 1908 Summer Olympics – Men's single sculls, time.event.locations, River Thames
River Thames, travel.tourist_attraction.near_travel_destination, Reading
Old London Bridge, base.architecture2.structure2.lead_designer, Isembert de Saintes
Structure, freebase.type_profile.strict_included_types, Topic
River Thames, book.book_subject.works, Three Men in a Boat
Greenwich foot tunnel, base.undergroundhumanthings.underground_object.underneath, River Thames
River Thames, common.topic.article, m.0d2l3
River Thames, common.topic.image, The Thames in London
Locale, rdf-schema#domain, Bridge
Bridges, rdf-schema#range, Bridge
Thames River, common.topic.notable_types, River
m.075rshc, common.webpage.resource, m.0bllbmn
m.049x405, location.adjoining_relationship.adjoins, River Thames
Isembert de Saintes, common.topic.notable_types, Architect
m.049x40w, location.adjoining_relationship.adjoins, River Thames
River Thames, location.location.adjoin_s, m.02_56pg
Frithuswith, people.person.place_of_birth, River Thames
Thames River, symbols.namesake.named_after, River Thames
England, location.location.containedby, United Kingdom
Old London Bridge, common.topic.webpage, m.075rshc
Great Synagogue of London, architecture.structure.architect, George Dance the Elder
George Dance the Elder, people.person.profession, Architect
Old London Bridge, people.place_of_interment.interred_here, Peter Colechurch
River Thames, location.location.people_born_here, Douglas Osborne
The Thames in London, common.image.appears_in_topic_gallery, River Thames
Lot's Ait, geography.island.body_of_water, River Thames
Isleworth Ait, location.location.containedby, United Kingdom
Three Men in a Boat, book.written_work.subjects, England
Kent, location.location.events, Caesar's invasions of Britain
m.075rshc, common.webpage.category, Topic Webpage
Architect, freebase.type_profile.published, Published
Chronicles of London bridge, book.written_work.author, Richard Thomson
Isembert de Saintes, people.person.gender, Male
Structure, freebase.type_profile.published, Published
Rowing at the 1908 Summer Olympics – Men's coxless pair, time.event.locations, River Thames
River Thames, location.location.adjoin_s, m.049x40q
River, freebase.type_hints.included_types, Topic
Old London Bridge, common.topic.article, m.075rt7z
Rhona Haszard, people.person.place_of_birth, River Thames
George Dance the Elder, people.person.children, George Dance the Younger
Bridge, freebase.type_hints.included_types, Topic
France, location.location.containedby, Europe
River Thames, geography.river.mouth, Thames Estuary
Demolition, common.topic.image, PerthOldMyerBuildingAnim gobeirne
River Thames, geography.river.mouth_long_lat, m.04njpy_
Isembert de Saintes, people.person.profession, Monk
Old London Bridge, book.book_subject.works, Chronicles of London bridge
Locale, type.property.schema, Bridge
Lot's Ait, location.location.containedby, United Kingdom
Reading, location.location.containedby, England
St Botolph-without-Bishopsgate, architecture.structure.architect, George Dance the Elder
London, base.biblioness.bibs_topic.is_really, London
River Thames, geography.body_of_water.islands, Isleworth Ait
Book, freebase.type_profile.strict_included_types, Topic
River, freebase.type_profile.strict_included_types, Location
River Thames, location.location.events, Above the Below
Nonesuch House, common.topic.notable_for, g.1259145yf
River Thames, location.location.events, Battle of the Kentish Knock
Bridge, freebase.type_hints.included_types, Location
River Thames, location.location.containedby, Europe
River Thames, common.topic.notable_types, River
St Botolph-without-Bishopsgate, location.location.containedby, United Kingdom
Brentford Ait, geography.island.body_of_water, River Thames
River Thames, location.location.adjoin_s, m.049x3_k
Nonesuch House, common.topic.notable_types, Location
Maidenhead, location.location.containedby, England
River, freebase.type_hints.included_types, Location
River Thames, common.topic.notable_for, g.1257z5x06
St Leonard's, Shoreditch, architecture.structure.architect, George Dance the Elder
River Thames, location.location.adjoin_s, m.046x0hs
Adventures by Disney - England and France Vacation, travel.tour_operator.travel_destinations, London
Chiswick Eyot, geography.island.body_of_water, River Thames
France, location.location.primarily_containedby, Europe
Total Length, type.property.schema, Bridge
Peter Colechurch, people.person.gender, Male
River Thames, geography.body_of_water.islands, Isle of Sheppey
George Dance the Elder, common.topic.notable_types, Architect
Frog Island, London, location.location.containedby, United Kingdom
Reading, base.biblioness.bibs_location.country, United Kingdom
Location, freebase.type_profile.published, Published
George Dance the Elder, architecture.architect.structures_designed, St Botolph's Aldgate
England, location.country.capital, London
Isembert de Saintes, people.person.nationality, France
Architect, freebase.type_hints.included_types, Topic
Structure, freebase.type_profile.strict_included_types, Location
Lower Horse, geography.island.body_of_water, River Thames
Caesar's invasions of Britain, time.event.locations, River Thames
Kent, location.location.partiallycontains, m.0wg9n1x
Thames Head, common.topic.notable_types, Location
United Kingdom, base.aareas.schema.administrative_area.administrative_children, England
Bridge, type.type.properties, Longest Span
m.0wg9n1x, location.partial_containment_relationship.partially_contained_by, Kent
River Thames, geography.body_of_water.islands, Oliver's Island
River Thames, base.undergroundhumanthings.location_on_top_of_something_buried.underground_object, Woolwich foot tunnel
Old London Bridge (1616) by Claes Van Visscher, common.image.appears_in_topic_gallery, Old London Bridge
George Dance the Elder, people.person.children, Nathaniel Dance-Holland
River Thames, geography.body_of_water.islands, Lot's Ait
United Kingdom, base.locations.countries.continent, Europe
River Thames, geography.body_of_water.islands, Brentford Ait
Demolition, common.topic.article, m.02zrvv
River Thames, base.undergroundhumanthings.location_on_top_of_something_buried.underground_object, Thames Tunnel
Reading, travel.travel_destination.tourist_attractions, River Thames
Bridge, type.type.properties, Width
Lower Thames Crossing, base.proposedprojects.proposed_project.project_focus, River Thames
George Dance the Elder, common.topic.article, m.03f0v3
Woolwich foot tunnel, common.topic.notable_types, Structure
Reading, location.administrative_division.country, United Kingdom
m.04nrby2, location.adjoining_relationship.adjoins, River Thames
Old London Bridge, location.location.contains, Nonesuch House
River Thames, location.location.containedby, United Kingdom
Bridge, freebase.type_profile.strict_included_types, Location
London, location.location.partially_contains, River Thames
Henley-on-Thames, location.location.containedby, United Kingdom
England, base.biblioness.bibs_location.country, United Kingdom
River Thames, geography.body_of_water.islands, Two Tree Island
Henley-on-Thames, base.biblioness.bibs_location.country, England
River Thames, geography.body_of_water.islands, Frog Island, London
Demolition, base.schemastaging.context_name.pronunciation, g.125_ph0x0
Bridge, type.type.domain, Transportation
Henley-on-Thames, location.location.containedby, England
Mansion House, London, common.topic.notable_types, Structure
Bridge, type.type.expected_by, Bridges
Nonesuch House, location.location.containedby, Old London Bridge
Europe, location.location.partially_contains, France
m.09xltpj, common.webpage.topic, River Thames
m.0j9cnc0, projects.project_participation.participant, Isembert de Saintes
Old London Bridge, architecture.structure.architect, Isembert de Saintes
River Thames, travel.tourist_attraction.near_travel_destination, Maidenhead
Mansion House, London, architecture.structure.architect, George Dance the Elder
River Thames, geography.river.origin_long_lat, m.04njp_s
Lower Horse, location.location.containedby, United Kingdom
River Thames, common.topic.image, London Thames Sunset panorama - Feb 2008
Oliver's Island, location.location.containedby, United Kingdom
Peter Colechurch, common.topic.notable_types, Architect
London, location.location.containedby, United Kingdom
Bridge Type, rdf-schema#domain, Bridge
Adventures by Disney - England and France Vacation, travel.tour_operator.travel_destinations, River Thames
River Thames, geography.river.origin, Thames Head
Bridge, freebase.type_profile.kind, Definition
George Dance the Elder, architecture.architect.structures_designed, Old London Bridge
George Dance the Elder, common.topic.notable_for, g.1256fvbv_
Battle of the Kentish Knock, time.event.locations, River Thames
Peter Colechurch, common.topic.notable_for, g.125501b4m
Richmond, London, travel.travel_destination.tourist_attractions, River Thames
River Thames, geography.river.cities, London
Body Of Water Spanned, type.property.schema, Bridge
Kent, location.location.partially_contains, River Thames
River, freebase.type_profile.strict_included_types, Topic
Jimmy Clarken, people.person.place_of_birth, River Thames
London, location.location.containedby, England
River Thames, geography.body_of_water.islands, Lower Horse
Total Length, rdf-schema#domain, Bridge
River Thames, location.location.adjoin_s, m.0832slc
Europe, base.locations.continents.countries_within, United Kingdom
m.046x0hs, location.adjoining_relationship.adjoins, River Thames
Bridge, type.type.properties, Bridge Type
River Thames, geography.geographical_feature.category, River
River Thames, location.location.events, Marchioness disaster
Three Men in a Boat, book.written_work.subjects, River Thames
River Thames, location.location.adjoin_s, m.049x405
River, freebase.type_profile.published, Published
River Thames, base.proposedprojects.proposed_project_focus.projects, Lower Thames Crossing
Thames Tunnel, location.location.containedby, United Kingdom
Two Tree Island, location.location.containedby, United Kingdom
m.0832slc, location.adjoining_relationship.adjoins, River Thames
River Thames, location.location.partially_contained_by, m.0wg9n1x
James Dance, people.person.gender, Male
m.0bllbmn, common.resource.annotations, m.075rshc
Bridge, freebase.type_hints.included_types, Structure
Isembert de Saintes, projects.project_participant.projects, m.0j9cnc0
France, location.location.partially_containedby, Europe
River, freebase.type_profile.equivalent_topic, River
Bridge, type.type.properties, Body Of Water Spanned
Isle of Sheppey, location.location.containedby, Kent
George Dance the Elder, architecture.architect.structures_designed, St Leonard's, Shoreditch
George Dance the Elder, architecture.architect.structures_designed, Mansion House, London
m.09klvvm, base.ontologies.ontology_instance_mapping.freebase_topic, River Thames
Henley-on-Thames, travel.travel_destination.tourist_attractions, River Thames
Bridges, owl#inverseOf, Body Of Water Spanned
River Thames, location.location.containedby, England
Locale, type.property.expected_type, Location
Maidenhead, location.location.containedby, United Kingdom
Peter Colechurch, people.deceased_person.place_of_burial, Old London Bridge
London Thames Sunset panorama - Feb 2008, common.image.appears_in_topic_gallery, River Thames
Bridge, type.type.properties, Number of spans
George Dance the Elder, architecture.architect.structures_designed, Great Synagogue of London
Bridge, type.type.properties, Total Length
George Dance the Elder, people.person.nationality, England
River Thames, geography.river.origin, Thames Head
River Thames, symbols.name_source.namesakes, Thames River
m.075rt7z, common.document.content, m.075rt86
London, base.biblioness.bibs_location.country, United Kingdom
Bridges, type.property.reverse_property, Body Of Water Spanned
Book, freebase.type_profile.kind, Definition
Isembert de Saintes, base.architecture2.architectural_designer.structures_designed, Old London Bridge
Isle of Sheppey, geography.island.body_of_water, River Thames
Book, freebase.type_profile.published, Published
England, location.administrative_division.first_level_division_of, United Kingdom
m.049x400, location.adjoining_relationship.adjoins, River Thames
River Thames, location.location.adjoin_s, m.049x3tw
Jimmy Clarken, people.person.gender, Male
Monk, people.profession.people_with_this_profession, Peter Colechurch
m.075rshc, common.webpage.topic, Old London Bridge
Chronicles of London bridge, book.book.editions, Chronicles of London bridge

Answer: Thames Head