The long side of a put option has the right to sell the underlying asset to the counterparty at the strike price. For a put with a strike price of $50, in which of the following case would the buyer of the put option want to exercise the option?

A. At expiration, the underlying price is 60

B. At expiration, the underlying price is 50

C. At expiration, the underlying price is 40

D. The buyer of the put option would exercise the option regardless of the underlying price