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: Asbestos is a dangerous carcinogen. 
Sentence2: Asbestos causes cancer.
[A]: Asbestos


[Q]: Sentence1: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Sentence2: Fossils are the remains of prehistoric life.
[A]: fossils


[Q]: Sentence1: energy is used for heating a building by a heating system. 
Sentence2: the sun's rays can be used for heating a building by a heating system.
[A]:
building