Problem: What are the most important words?
He shifts his gaze to someone who continues to stare straight ahead with a stoic expression.
Answer: continue, gaze, stare

Problem: What are the most important words?
a flight ofaircraft model and aircraft fly in formation
Answer: aircraft, fly, model

Problem: What are the most important words?
small rocky island and lonely tree middle of the lake
Answer:
lake, middle, tree