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: Ice is frozen water. 
Sentence2: ice expands.

Answer: Ice


Question: Sentence1: dropping an object into water causes vibrations in the water. 
Sentence2: Dropping an object into lake causes vibrations.

Answer: dropping


Question: Sentence1: Flowers produce seeds for reproduction. 
Sentence2: A flowers purpose is to reproduce.

Answer:
reproduction