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: air pollution can cause the pH of soil to decrease. 
Sentence2: Acidity is measured with a pH meter or with pH paper strips.

Answer: pH


Question: Sentence1: triceps contracting causes a person 's elbow to straighten. 
Sentence2: muscles contracting cause a person's elbow to straighten.

Answer: contracting


Question: Sentence1: Plants use the sun's energy to transform carbon dioxide gas and water into a sugar called glucose. 
Sentence2: Ethanol production is reliant on the sun's energy.

Answer:
energy