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: a flashlight converts chemical energy into light energy. 
Sentence2: PALight Flashlights are the ultimate personal LED flashlights.
[A]: flashlight


[Q]: Sentence1: gases released during the use of fossil fuels causes global warming. 
Sentence2: Fossil fuels are coal, oil, and natural gas.
[A]:
fossil