问题如下：
The following statements are about the
methods of pricing deposits. Which of the following statement is NOT correct?
选项：
A.In the conditional pricing method, clients pay a low fee or no fee if the deposit balance remains above some minimum level but a higher fee if the average balance falls below that minimum.
B.Customers who purchase two or more services may be granted lower deposit fees compared to the fees charged customers having only a limited relationship to the offering institution.
C.One of the advantages of conditional pricing method is that the customer, not the offering institution, chooses which deposit plan is preferable.
D.In the marginal cost method, if interest rates are declining, the marginal cost must stay above the historical average cost.
解释：
考点：对Managing and Pricing Deposit Services的理解
答案：D
解析：
选项D错误，当利率降低时，Marginal
cost在Historical average cost之下。
D可以解释一下原因吗
