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: Interstellar space contains a plasma. 
Sentence2: interstellar space contains electrons, atoms, and stars.

Answer: Interstellar


Question: Sentence1: Populations Populations are subsets of a species. 
Sentence2: Gene flow occurs when individuals move into or out of a subset of a species.

Answer: species


Question: Sentence1: Mutation creates new genetic variation in a gene pool. 
Sentence2: Mutation creates biodiversity.

Answer:
Mutation