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: moss causes chemical weathering. 
Sentence2: Sphagnum moss mixed with peat moss.
[A]: moss


[Q]: Sentence1: Animals behave in a variety of ways which enhance their chances of survival and reproduction. 
Sentence2: Animals learn to behave to increase chances of survival.
[A]: behave


[Q]: Sentence1: Mammals generate heat mainly by keeping their metabolic rate high. 
Sentence2: mammals generate heat by consuming calories.
[A]:
Mammals