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: being burried under soil and mud changes peat into coal through extreme heat and pressure in a swamp over a long period of time. 
Sentence2: Marble is used for sculptures, and coal is used for fuel and energy like light.
[A]: coal


[Q]: Sentence1: Scientists still know relatively little about Archaea. 
Sentence2: scientists still know relatively little about non-bacterial prokaryotes.
[A]: Scientists


[Q]: Sentence1: fire converts chemical energy into light and heat energy. 
Sentence2: Lightning is also a cause of fires.
[A]:
fire