Problem: What are the most important words?
the sky turns pink as a rainbow appears at dusk after a thunderstorm .
Answer: appear, rainbow, thunderstorm

Problem: What are the most important words?
why buying the most expensive motorcycle on internet publishing and broadcasting and web search portals business saved me money
Answer: business, buy, money, save

Problem: What are the most important words?
a large bouquet of various flowers and berries
Answer:
berry, bouquet, flower