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: Moisture is required for the microorganisms to grow. 
Sentence2: Moisture can cause infections to grow.

A: Moisture
****
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: Ethologists usually study how animals behave in their natural environment. 
Sentence2: ethologists usually study how animals behave in their habitat.

A:
Ethologists
****