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.

Q: Sentence1: Batteries are a better source of DC electricity. 
Sentence2: a flashlight requires batteries to produce light.

A: Batteries
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Q: Sentence1: Organisms cluster around hydrothermal vents in the ocean floor. 
Sentence2: vents on the ocean floor are powered by heat.

A: vents
****
Q: Sentence1: Cats are Mammals that Shed Dogs are Mammals that Wag their tails. 
Sentence2: Playing is just one of many ways that dogs learn to behave.

A:
Dogs
****