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: Amphibians have permeable skin that easily absorbs substances from the environment. 
Sentence2: Some substances are harmful to the body and block biological systems.

Answer: substances


Question: Sentence1: Lions live in social groups called prides. 
Sentence2: Chimpanzees live in social groups called communities.

Answer: groups


Question: Sentence1: All animals are heterotrophs. 
Sentence2: all alligators are heterotrophs.

Answer:
All