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: Lions live in social groups called prides. 
Sentence2: Chimpanzees live in social groups called communities.

Answer: groups


Question: Sentence1: folding an object causes that object to change shape. 
Sentence2: Folding an object causes that object to transform.

Answer: causes


Question: Sentence1: Paleontologists build fires with natural vegetation. 
Sentence2: Scientists who find and study fossils build fires with natural vegetation.

Answer:
build