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

Answer: dropping


Question: Sentence1: skin is used for protecting the body from harmful substances. 
Sentence2: Acids are harmful to tissue.

Answer: harmful


Question: Sentence1: Earthworm burrows help aerate soil, which is also good for plants. 
Sentence2: Earthworms are perhaps the most familiar decomposer.

Answer:
Earthworm