Problem: What are the most important words?
roots of a fallen tree extend skyward where a brook empties into a lake .
Answer: extend, lake, tree

Problem: What are the most important words?
protected site in the winter time
Answer: protect, site, time

Problem: What are the most important words?
sun rising through a thick fog in the very early morning over a field of round hay bales
Answer:
fog, morning, rise, sun