Which of These Is an Instance of a Quasi-Contract

Multiple Choice

Which of these is an instance of a quasi-contract?

A) an employee receiving his or her paycheck every month
B) an unconscious man being nursed by a hospital, having been brought in by a passer-by
C) two companies signing a business agreement that spans an undefined duration
D) a woman hiring a caterer only after the caterer promises to deliver the food on time