Problem: What are the most important words?
revellers celebrate the new year and ethnicity festival against a dark sky
Answer: celebrate, festival, year

Problem: What are the most important words?
The dog is burying the bone.
Answer: bone, bury, dog

Problem: What are the most important words?
an astronaut drifting in space is rescued by a space shuttle orbiting earth
Answer:
astronaut, drift, earth, orbit, space