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: Competition may lead to aggressive behaviors or displays of aggression. 
Sentence2: Aggression Aggression and violence often go together.
[A]: aggression


[Q]: Sentence1: conserving water can be used for survival in a dry environment. 
Sentence2: conserving water can be used for survival in deserts.
[A]: conserving


[Q]: Sentence1: All oaks are trees. 
Sentence2: if an oak falls then sunlight becomes available to the surrounding plants.
[A]:
oaks