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: Cells are the units of function in living things. 
Sentence2: living things cannot survive without oxygen.
[A]: living


[Q]: Sentence1: Interestingly, a squid is also a mollusk. 
Sentence2: squids have a circulatory system with one or two hearts that pump blood.
[A]: squid


[Q]: Sentence1: an egg requires warmth to survive. 
Sentence2: An egg will hatch if it survives.
[A]:
egg