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: Carpools and vanpools can save time. 
Sentence2: vanpools decrease the amount of cars used to travel to a place.

A: vanpools
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Q: Sentence1: Plants use unsaturated fatty acids to store energy. 
Sentence2: Plants and fish contain fatty acids.

A: Plants
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Q: Sentence1: All life relies on a relatively narrow range of pH, or acidity. 
Sentence2: If the pH level is higher or lower, aquatic life is endangered.

A:
pH
****