参考答案：C

解析：

If marginal cost is above the average cost, when you produce your next unit, average cost will increase. Because marginal cost is the cost of producing the next unit, and because this cost is above the firm's average cost per unit, the average cost per unit must increase, if only slightly. Based on the information provided in the question, there is no way to know what will happen to the marginal cost of future units produced.