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: forming coal requires decaying vegetation. 
Sentence2: Forming fossil fuels requires decaying vegetation.

Answer: decaying


Question: Sentence1: a battery converts chemical energy into electrical energy. 
Sentence2: A battery produces a flow of electrons.

Answer: battery


Question: Sentence1: a plant requires sunlight for photosynthesis. 
Sentence2: For plants to photosynthesize, they require electromagnetic energy.

Answer:
photosynthesis