Problem: What are the most important words?
time lapse of clouds floating over a mountain during the day
Answer: cloud, day, float

Problem: What are the most important words?
Large tray of vegetables, carrots, potatoes, sprouts and radish.
Answer: carrot, potato, tray

Problem: What are the most important words?
hundreds of fans had been waiting for over a day to see rhythm and blues artist
Answer:
day, fan, hundred, wait