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.

Q: Sentence1: smell is used for finding food by some animals. 
Sentence2: Food includes small rodents and birds.

A: food
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Q: Sentence1: Smoking accelerates the aging process. 
Sentence2: smoking accelerates the death of cells.

A: Smoking
****
Q: Sentence1: Androgens are male sex hormones. 
Sentence2: androgens are chemical messengers.

A:
Androgens
****