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: Most pituitary hormones control other endocrine glands. 
Sentence2: Hormones tell the ovaries to produce eggs.

Answer: hormones


Question: Sentence1: Bird eggs have hard, calcium carbonate shells. 
Sentence2: The reproductive cells of a bird is a hard, calcium carbonate shell.

Answer: calcium


Question: Sentence1: Raw coal can be burned to produce electricity. 
Sentence2: coal can cause a wire to heat up.

Answer:
coal