Question: What is the official website of the organization that maintains National Register of Historic Places?
Choices: http://ImogenHeap.com
http://www.katebush.com
https://www.comune.roma.it/
http://www.co.madison.il.us
http://www.nps.gov/
https://www.miramax.com/movie/spy-kids-3-d-game-over/
http://www.mercercounty.org
https://www.lafayetteltravel.com
http://www.sonypictures.com/movies/gattaca/
http://www.locusmag.com/SFAwards/Db/Locus.html
SPARQL: SELECT DISTINCT ?pv WHERE { ?e <pred:instance_of> ?c . ?c <pred:name> "organization" . ?e_1 <maintained_by> ?e . ?e_1 <pred:name> "National Register of Historic Places" .  ?e <official_website> ?pv .  }
Program:
function: Find
inputs: National Register of Historic Places
function: Relate
dependencies: 0
inputs: maintained by
forward
function: FilterConcept
dependencies: 1
inputs: organization
function: QueryAttr
dependencies: 2
inputs: official website
Answer: http://www.nps.gov/