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: Flies are insects with two wings. 
Sentence2: Flies are arthropods with two wings.

A: Flies
****
Q: Sentence1: if an object is black then that object absorbs all visible light. 
Sentence2: Light grains are quartz, Black grains are coal.

A:
black
****