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: Carbon cycles quickly between organisms and the atmosphere. 
Sentence2: the atmosphere is essential to all living organisms.

Answer: organisms


Question: Sentence1: triceps contracting causes a person 's elbow to straighten. 
Sentence2: Triceps stretch Stretches muscles in back of upper arm.

Answer:
triceps