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: Coral reefs provide food and shelter to many ocean organisms. 
Sentence2: Coral Reefs Coral reefs are threatened.

A: Coral
****
Q: Sentence1: Here, the lungs supply the blood with oxygen. 
Sentence2: Brain cells die quickly if their blood supply is cut off.

A: blood
****
Q: Sentence1: protein is used to repair cells by the human body. 
Sentence2: Meat, fish and chicken are rich sources of protein.

A:
protein
****