What are the keywords in the following sentence? posters hanging on the wall above the green couch
couch, hang, wall

What are the keywords in the following sentence? A giraffe at the zoo walking across his cage.
cage, giraffe, walk, zoo

What are the keywords in the following sentence? the traditional trams running round city centre
centre, run, tram

What are the keywords in the following sentence? Sheep in field by barn with fence and car.
barn, fence, field, sheep