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: high mountains with well-rounded peaks can be formed by collision of crustal plates. 
Sentence2: high mountains with well-rounded peaks can be formed by collision of plate tectonics.

Answer: collision


Question: Sentence1: a polar bear requires a cold environment. 
Sentence2: polar bears live where there are fewer animals.

Answer: bear


Question: Sentence1: Gymnosperms are vascular plants that produce seeds in cones. 
Sentence2: Gymnosperms produce conifers.

Answer:
Gymnosperms