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: Without light there is no sense of vision. 
Sentence2: Glass causes a sense of vision.

Answer: sense


Question: Sentence1: Animals behave in a variety of ways which enhance their chances of survival and reproduction. 
Sentence2: Animals learn to behave to increase chances of survival.

Answer: behave


Question: Sentence1: Viruses cannot reproduce by themselves. 
Sentence2: Herpes simplex virus is one member in the herpes group of viruses.

Answer:
Viruses