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.

[EX Q]: Sentence1: a flashlight converts chemical energy into light energy. 
Sentence2: Chemical energy converted to light energy requires batteries.
[EX A]: chemical

[EX Q]: Sentence1: protein is used to repair cells by the human body. 
Sentence2: Wound healing requires protein.
[EX A]: protein

[EX Q]: Sentence1: All fish have gills . 
Sentence2: All fish breathe water.
[EX A]:
All