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: keeping food cold is used for keeping food fresh. 
Sentence2: Keeping food at 40 degrees F or lower is used for keeping food fresh.

Answer: food


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

Answer: temperature


Question: Sentence1: An X-ray is a negative image. 
Sentence2: negative images are used in medical technology.

Answer:
image