单选题 For a natural monopoly, the optimal policy for a regulator to set is a price such that ______.

A、 The price level equals marginal cost.
B、 The price level equals average variable cost.
C、 The price level equals average total cost but higher than marginal cost.
D、 The price level is lower than marginal cost but higher than average total cost.

【正确答案】 C

【答案解析】[解析] 对于自然垄断行业，监管机构的最优定价策略是价格高于边际成本，等于平均成本。