Question: 7/7 Ripple Effect is a 57-minute homemade film produced and narrated under the pseudonym "Muad'Dib", the film disputes the official account of the 7 July 2005 London bombings (also known as 7/7), a terrorist attack on public transport in Central London, by four suicide bombers, including Germaine Maurice Lindsay, also known as Abdullah Shaheed Jamal, was one of the four terrorists who detonated bombs, on how many trains?

Context paragraphs:
Reactions to the 2005 London bombings: The 7 July 2005 London bombings were a series of suicide attacks carried out by homegrown terrorists on London's public transport network during the morning rush hour.

Operation Kratos: Operation Kratos referred to tactics developed by London's Metropolitan Police Service for dealing with suspected suicide bombers, most notably firing shots to the head without warning.  The tactics were developed shortly after the 11 September 2001 attacks, based in part on consultation with Israeli and Sri Lankan law enforcement agencies on how to deal with suicide bombers.  Little was revealed about these tactics until after the mistaken shooting of Jean Charles de Menezes on 22 July 2005, in the wake of the 7 July 2005 London bombings.  The term is no longer used by the Metropolitan Police, although similar tactics remain in force.

Hasib Hussain: Hasib Mir Hussain (Urdu: حسیب میر حسین‎ ; 16 September 1986 – 7 July 2005) was one of four terrorists who detonated bombs on three trains on the London Underground and one bus in central London during the 7 July 2005 London bombings.

Mohammad Sidique Khan: Mohammad Sidique Khan (20 October 1974 – 7 July 2005) was the oldest of the four homegrown suicide bombers and believed to be the leader responsible for the 7 July 2005 London bombings, in which bombs were detonated on three London Underground trains and one bus in central London suicide attacks, killing 56 people including the attackers and injured over 700.  Khan bombed the Edgware Road train killing himself and six other people.

7/7 Ripple Effect: 7/7 Ripple Effect is a 57-minute homemade film produced and narrated under the pseudonym "Muad'Dib", who was later named by the BBC as conspiracy theorist John Hill.  The film disputes the official account of the 7 July 2005 London bombings (also known as 7/7), a terrorist attack on public transport in Central London, by four suicide bombers later named as Hasib Hussain, Germaine Lindsay, Shehzad Tanweer, and Mohammad Sidique Khan.

7 July 2005 London bombings: The 7 July 2005 London bombings, often referred to as 7/7, were a series of coordinated terrorist suicide bomb attacks in London, United Kingdom, which targeted civilians travelling on the city's public transport system during the morning rush hour.

List of marauding terrorist incidents: This is a list of marauding terrorist incidents.  Marauding terrorist incidents refers to terrorist incidents which occur across multiple sites and perpetrated by the same attacker or group of attackers where firearms are the principle weapon.  Not included are car bomb attacks, there is a separate list for attacks using car bombs unless attackers also used firearms in the attacks.  Mass suicide bombings such as the 7 July 2005 London bombings will not be counted either, unless there are firearms used in the attacks.

21 July 2005 London bombings: On Thursday 21 July 2005, four attempted bomb attacks disrupted part of London's public transport system two weeks after the 7 July 2005 London bombings.  The explosions occurred around midday at Shepherd's Bush, Warren Street and Oval stations on the London Underground, and on a bus in Bethnal Green.  A fifth bomber dumped his device without attempting to set it off.

Shehzad Tanweer: Shehzad Tanweer (15 December 1982 – 7 July 2005) was one of four men who detonated explosives in three trains on the London Underground and one bus in central London during the 7 July 2005 London bombings.  52 people were killed and over 700 wounded in the attacks.

Germaine Lindsay: Germaine Maurice Lindsay (23 September 1985 – 7 July 2005), also known as Abdullah Shaheed Jamal, was one of the four terrorists who detonated bombs on three trains on the London Underground and a bus in central London during the 7 July 2005 London bombings, killing 56 people (including themselves), and injuring more than 700.  Lindsay detonated the bomb that killed himself and 26 other people on a train travelling on the Piccadilly line between the King's Cross and Russell Square tube stations.

Supporting paragraphs: 7/7 Ripple Effect Germaine Lindsay
Answer: three