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: protein is used to repair cells by the human body. 
Sentence2: Meat, fish and chicken are rich sources of protein.

A: protein
****
Q: Sentence1: Flies are insects with two wings. 
Sentence2: Flies are arthropods with two wings.

A: Flies
****
Q: Sentence1: Public Transportation systems move people. 
Sentence2: transportation is used for moving things.

A:
move
****