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: an animal requires air for survival. 
Sentence2: It is breathed in by animals and restored to the air by the photosynthesis mechanism of plants.
[A]: air


[Q]: Sentence1: Precipitation falls on the windward side of the mountain range. 
Sentence2: Mountains have higher precipitation than adjacent lowlands.
[A]: Precipitation


[Q]: Sentence1: recycling has a positive impact on the environment. 
Sentence2: certain Steel products have a positive impact on the environment.
[A]:
environment