Problem: What are the most important words?
The man is clearing brush from a forest.
Answer: brush, clear, forest

Problem: What are the most important words?
blossom with king flowers open pink bud in an orchard
Answer: bud, flower, open

Problem: What are the most important words?
volcanic activity under meromictic lake produced a cloud of carbon dioxide that asphyxiated villagers
Answer:
asphyxiate, cloud, dioxide, lake, villager