For Which of the Following Reasons Do Regulatory Agencies Sometimes

For which of the following reasons do regulatory agencies sometimes fail to bring the price and output of a natural monopoly to the ideal level?

A) The regulatory agency does not have all the information concerning a firm's true costs.
B) Monopolists may conceal profits by inflating the costs of production by spending money to achieve personal objectives (a very nice office building, for example) .
C) Regulatory agencies often come to reflect the views of the industries they are supposed to regulate.
D) All of the above are reasons.