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: faulting of rock in Earth 's crust causes earthquakes. 
Sentence2: fault movement forms earthquakes.
[A]: earthquakes


[Q]: Sentence1: a polar bear requires a cold environment. 
Sentence2: polar bears live where there are fewer animals.
[A]: bear


[Q]: Sentence1: Roundworms make up the phylum Nematoda. 
Sentence2: Roundworms contribute to soils.
[A]:
Roundworms