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: Mad Cow disease is a concern. 
Sentence2: pathogens can cause Mad Cow.

A: Cow
****
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: gases from burning coal and oil dissolving in water in the atmosphere causes acid rain. 
Sentence2: Acid rain can destroy soil.

A:
acid
****