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 fire requires oxygen to burn. 
Sentence2: A fire requires something with exactly eight protons to burn.

Answer: burn


Question: Sentence1: exercise increases a body 's strength. 
Sentence2: Exercise is more than running and lifting.

Answer: exercise


Question: Sentence1: Viruses contain DNA but not much else. 
Sentence2: smallpox contains DNA but not much else.

Answer:
DNA