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: Instead, the body is covered with a protective shell of bony armor. 
Sentence2: Most mollusks have protective of bony armor.

Answer: armor


Question: Sentence1: Cells are the microscopic building blocks of organisms. 
Sentence2: proteins are the building blocks of organisms.

Answer: organisms


Question: Sentence1: Earth 's tilt on its rotating axis causes seasons to change. 
Sentence2: Earth's tilt causes winter.

Answer:
Earth