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: a polar bear requires a cold environment. 
Sentence2: polar bears live where there are fewer animals.

Answer: bear


Question: Sentence1: Average vehicle speed rises by only 0.3 miles per hour. 
Sentence2: a speedometer measures miles per hour.

Answer: hour


Question: Sentence1: Among the small inorganic molecules which are economically attractive are CO and H 2 . 
Sentence2: Producers make food from CO and H 2.

Answer:
2