If the Demand Curve Facing a Monopolist Shifts, Then the Monopolist's

If the demand curve facing a monopolist shifts, then the monopolist's:

A) marginal revenue curve and profit-maximizing level of output will change.
B) marginal revenue curve will not change, but its profit-maximizing level of output will.
C) total cost curve will change, but its variable cost curve will not.
D) marginal revenue curve will change, but its profit-maximizing level of output will not.