The Writer of a Put Option

The writer of a put option

A) has the right, but not the obligation, to sell shares of the underlying asset.
B) has the right, but not the obligation, to buy shares of the underlying asset.
C) is obliged to buy shares of the underlying asset if the put holder chooses to exercise the option.
D) is obliged to sell shares of the underlying asset if the put holder chooses to exercise the option.