For a monopolist, as demand changes, this will lead to changes in:

a. Price with no change in output,

b. Both price and quantity,

c. Output with no change in price,

d. Any of the choices can be true.

B. Both price and quantity

Reason: When there is any change in demand of the monopoly, the demand curve or the average revenue curve will either shift to the right or left, making changes in both quantity and price in the market. If there is increase in demand, it will make the AR and MR curve to shift rightwards leading to increase in both price and quantity. Similarly when the demand decreases, the AR and MR curve will shift to the left, making both price and quantity to decrease.