Marginal Cost Regulatory Pricing Turns Out to Be the Same

Marginal cost regulatory pricing turns out to be the same as output regulation (for a natural monopoly firm) if the output level set by government is the

A) amount at which marginal cost equals average total cost.
B) resource-allocative efficient amount.
C) amount at which average total cost is at its highest level.
D) amount at which marginal revenue equals marginal cost.