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: 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.
[EX A]: coal

[EX Q]: Sentence1: an image in a mirror is formed by reflecting light. 
Sentence2: mirrors can be seen with our eyes.
[EX A]: mirror

[EX Q]: Sentence1: when a metal rusts , that metal becomes orange on the surface. 
Sentence2: Iron rusts in the presence of oxygen and water.
[EX A]:
rusts