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 plant requires sunlight to grow. 
Sentence2: Grass needs air and sunlight.

Answer: sunlight


Question: Sentence1: friction causes the temperature of an object to increase. 
Sentence2: pressure causes the temperature of an object to increase.

Answer: causes


Question: Sentence1: shelter is used for protection by animals against weather. 
Sentence2: Trees provide animals protection against the weather.

Answer:
against