instruction:
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.
question:
Sentence1: protein is used to repair cells by the human body. 
Sentence2: Meat, fish and chicken are rich sources of protein.
answer:
protein


question:
Sentence1: a wildfire changes an ecosystem drastically. 
Sentence2: Forest fires change an ecosystem drastically.
answer:
changes


question:
Sentence1: a beak is used for catching prey by some birds. 
Sentence2: A bill is used for catching prey by some birds.
answer:

a