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: Cells are the microscopic building blocks of organisms. 
Sentence2: proteins are the building blocks of organisms.

Answer: organisms


Question: Sentence1: gills are used for breathing water by aquatic animals. 
Sentence2: gills are used for breathing water by sharks.

Answer: are


Question: Sentence1: if an object is kicked then force is exerted on that object. 
Sentence2: Acceleration of an object is proportional to the force acting on that object.

Answer:
force