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: Most water comes from precipitation. 
Sentence2: aquatic animals require precipitation to survive.

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

A: Smoking
****
Q: Sentence1: Loss of ozone has created an ozone hole over Antarctica. 
Sentence2: Ozone and CFCs are greenhouse gases.

A:
ozone
****