Problem: What are the most important words?
a city provides critical habitat for threatened species such as polar bears .
Answer: city, habitat, provide

Problem: What are the most important words?
the old building after the congregation had moved out and turned it over .
Answer: building, congregation, move

Problem: What are the most important words?
The bowl has a half a grapefruit and the plate has donut and the other half.
Answer:
grapefruit, half, plate