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: riding a bike does not cause pollution. 
Sentence2: riding a bike does not release particles.
[A]: bike


[Q]: Sentence1: if fossils of an animal or plant are found in a place then that animal or plant used to live in that place. 
Sentence2: Fossils are preserved original remains or preserved evidence of plants and animals.
[A]: fossils


[Q]: Sentence1: coal is used for generating heat by burning. 
Sentence2: Heat comes out the top and can be used for cooking or space heating.
[A]:
heat