Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
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Question: Sentence1: a greenhouse is used to protect plants by keeping them warm. 
Sentence2: Flower size varies by plant.

Answer: plants


Question: Sentence1: friction causes the temperature of an object to increase. 
Sentence2: internal combustion engines get hot.

Answer: temperature


Question: Sentence1: if a planet becomes too hot then that planet cannot sustain life. 
Sentence2: Venus is the hottest planet.

Answer:
hot