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: June Summer Triangle Three bright stars light up the summer sky. 
Sentence2: Nuclear reactions in stars cause them to brighten up the summer sky.
[A]: bright


[Q]: Sentence1: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.
[A]: bacteria


[Q]: Sentence1: Any antigen that causes an allergy is called an allergen. 
Sentence2: pollens are antigens that can cause an allergy.
[A]:
allergy