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: Female monotremes lack a uterus and vagina. 
Sentence2: Babies are normally delivered from the uterus through the vagina.

SOLUTION: uterus

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

SOLUTION: blood

PROBLEM: Sentence1: Beaks and bills Instead of a mouth, birds have a hard beak or bill. 
Sentence2: A bill is used for catching prey by some birds.

SOLUTION:
bills