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: All photos are digital images. 
Sentence2: satellites are used to take photos from space.
[A]: photos


[Q]: Sentence1: a battery converts chemical energy into electrical energy. 
Sentence2: A battery produces a flow of electrons.
[A]: battery


[Q]: Sentence1: Earthquakes Earthquakes Japan is an earthquake-prone country. 
Sentence2: Japan has a lot of mountains.
[A]:
Japan