Given a passage and a question, find the answer to the question based on the passage. The answer should consist of only one word that lies in the span of only one of the sentences in the passage.

[EX Q]: Paragraph: Karen Gillan ( born 28 November 1987 ) is a Scottish actress , director , screenwriter and model . She played the role of Amy Pond , companion to the Eleventh Doctor , in the BBC One science fiction series Doctor Who ( 2010 -- 2013 ) . She has received wide recognition for portraying Nebula in the Marvel Cinematic Universe films Guardians of the Galaxy ( 2014 ) , Guardians of the Galaxy Vol. 2 ( 2017 ) , Avengers : Infinity War ( 2018 ) , and its untitled sequel ( 2019 ) , and also played Ruby Roundhouse in the box - office hit Jumanji : Welcome to the Jungle ( 2017 ) .
Question: who does karen gillian play in the avengers

[EX A]: Nebula

[EX Q]: Paragraph: The European Union is a sui generis supranational union possessing `` country - like '' characteristics . The entity is composed of 28 member countries . Its population density has been estimated at 116 people per km , and it would be ranked 95th if it were included in the list . ( population : 506,913,394 on January 1 , 2014 , area : 4,324,782 km ) . See also : List of regional organizations by population . The most densely populated sovereign nation is Monaco , with a population density of 18,713 people / km . Area includes land and water .
Question: country with highest population density per square mile

[EX A]: Monaco

[EX Q]: Paragraph: Aqueducts moved water through gravity alone , along a slight overall downward gradient within conduits of stone , brick , or concrete ; the steeper the gradient , the faster the flow . Most conduits were buried beneath the ground and followed the contours of the terrain ; obstructing peaks were circumvented or , less often , tunneled through . Where valleys or lowlands intervened , the conduit was carried on bridgework , or its contents fed into high - pressure lead , ceramic , or stone pipes and siphoned across . Most aqueduct systems included sedimentation tanks , which helped reduce any water - borne debris . Sluices and castella aquae ( distribution tanks ) regulated the supply to individual destinations . In cities and towns , the run - off water from aqueducts scoured the drains and sewers .
Question: what force did the romans use to move water

[EX A]:
gravity