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.

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.
air

Sentence1: an animal requires air for survival. 
Sentence2: The Moon has no atmosphere and no air.
air

Sentence1: sugar causes food to taste sweet. 
Sentence2: Molasses Sugar Molasses Sugar is the darkest sugar of all.

sugar