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: the ovaries are used in reproduction. 
Sentence2: Unlike most female animals, which have two functioning ovaries, the chicken usually has only one.
[A]: ovaries


[Q]: Sentence1: a flashlight converts chemical energy into light energy. 
Sentence2: Only as long as there are batteries in the flashlight, the flashlight will function.
[A]: flashlight


[Q]: Sentence1: astronauts require preserved food for extended flights. 
Sentence2: Space travel is for trained astronauts only.
[A]:
astronauts