Should a Firm Always Produce the Level of Output Where

Should a firm always produce the level of output where marginal cost is lowest?

A) Yes, that is the level of output where costs are lowest.
B) No, that is the level of output where employees are most efficient.
C) No, firms should produce where marginal cost equals average cost.
D) No, that might be the best choice, but it depends on the firm's profits.
E) Yes, any other level of output will have higher marginal cost.