Which of the Following Is True

Which of the following is true?

A) Average cost pricing reduces the incentives for a monopolist to find ways to reduce its costs.
B) With natural monopoly, if regulators allow the firm to earn profits, there will be a welfare cost from producing too little of the good.
C) Government regulation of monopolies aims to achieve the efficiency of large-scale production, without permitting the producers to charge monopoly prices.
D) All of the above are true.