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: Heterotrophs get food by eating other living things. 
Sentence2: fish eat other living things.

A: living
****
Q: Sentence1: All life relies on a relatively narrow range of pH, or acidity. 
Sentence2: humans rely on a relatively narrow range of acidity.

A: acidity
****
Q: Sentence1: Hearing requires functioning ears. 
Sentence2: ears are used for sensing sound by animals.

A:
ears
****