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: Urine leaves the body through a sphincter in the process of urination. 
Sentence2: urine leaves the body upon relaxation of a muscle.

A: Urine
****
Q: Sentence1: a thermometer is used to measure temperature. 
Sentence2: a thermometer is used to measure heat.

A: a
****
Q: Sentence1: Any surface that has not been sterilized is likely to be covered with bacteria. 
Sentence2: Any surface that has not been sterilized is likely to be covered with single cell microorganisms.

A:
covered
****