Problem: What are the most important words?
Two airplanes with propellers on the tarmac.
Answer: airplane, propeller, tarmac

Problem: What are the most important words?
visitors rummage for bargains on the flea market in industry in town centre
Answer: centre, market, visitor

Problem: What are the most important words?
barges travel on a hazy day .
Answer:
barge, day, travel