问题如下：
Due to market change, the product price of a firm is declining significantly. To survive and operate in the short run, the firm should:
选项：
A. control the marginal cost at least lower than price.
B. control the average total cost at least lower than price.
C. control the average variable cost at least lower than price
解释：
C is correct.
In the short run, the firm will continue to operate as long as it is able to cover part of the fixed cost. Therefore the firm should control the average variable cost at least lower than price
考点：盈亏平衡点
解析：在短期内，只要公司盈利超过可变成本，并挽回部分固定成本，它就会继续运营。因此，厂商的售价要大于平均可变成本。
为什么不是A，边际成本大于市场价格，证明再生产一单位产品就要亏损