Problem: What are the most important words?
ancient geologic events may have left deep that can come to life and play a role in earthquakes .
Answer: come, event, leave

Problem: What are the most important words?
freight train rounds a bend in hills above us state
Answer: bend, hill, round, state, train

Problem: What are the most important words?
a shoal of small tropical fish off island
Answer:
fish, island, shoal