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: With a spatula, fold in flour mixture. 
Sentence2: a sifter is used for separating flour.
[A]: flour


[Q]: Sentence1: Algae have varied life cycles. 
Sentence2: And fish eat algae.
[A]: Algae


[Q]: Sentence1: Playing is just one of many ways that mammals and other animals learn how to behave. 
Sentence2: mammal learn to behave by having fun.
[A]:
behave