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: Smoking accelerates the aging process. 
Sentence2: smoking accelerates the death of cells.

Answer: Smoking


Question: Sentence1: microscope is used to see small things by biologists by making them appear bigger. 
Sentence2: Something invented by Leeuwenhoek is used to see small things by biologists by making them appear bigger.

Answer: appear


Question: Sentence1: Food is fuel and energy. 
Sentence2: Running requires a lot of fuel.

Answer:
fuel