TASK DEFINITION: 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.
PROBLEM: Sentence1: protein is used to repair cells by the human body. 
Sentence2: Meat, fish and chicken are rich sources of protein.

SOLUTION: protein

PROBLEM: Sentence1: Any antigen that causes an allergy is called an allergen. 
Sentence2: Antigens are proteins foreign to the body.

SOLUTION: antigen

PROBLEM: Sentence1: Human papillomavirus vaccine is aimed at the cause of most cases of cervical cancer. 
Sentence2: A vaccine against a virus can protect against cervical cancer.

SOLUTION:
cervical