6. Recent audits revealed that BanqueCard, a credit service, has erred in calculating the interest it charges its clients. But BanqueCard’s chief accountant reasoned that the profits that the company shows would remain unaffected by a revision of its clients’ credit statements to correct its previous billing errors, since just as many clients had been overcharged as undercharged.

Which of the following is a reasoning error that the accountant makes in concluding that correcting its clients’ statements would leave BanqueCard’s profits unaffected?

(A) Relying on the reputation of BanqueCard as a trustworthy credit service to maintain the company’s clientele after the error becomes widely known

(B) Failing to establish that BanqueCard charges the same rates of interest for all of its clients

(C) Overlooking the possibility that the amount by which BanqueCard’s clients had been overcharged might be greater than the amount by which they had been undercharged

(D) Assuming that the clients who had been overcharged by BanqueCard had not noticed the error in their credit bills（C）

(E) Presupposing that each one of BanqueCard’s clients had either been overcharged or else had been undercharged by the billing error

我做的时候本选从c，后来觉得e更忠实于题干才选的e，没想到答案是c，如何排除e？是因为 presupposing错了吗

看懂题意:公司不会受益,因为被overcharge的人和被undercharge人一样多.

区别C , E应该没问题吧

B与题目无关.
题干说有些人被多要钱了(该收他20块,结果收了30块),有些人被少要钱了(该要30块,只被收了20块).
所以问题的就是少要的那部分钱是不是和多要的那部分钱刚好相抵消,跟rate没有任何关系

可是题干说：BC的会计认为undercharge和overcharge的人数相同，因此其profit不变。所以我觉得如果interest rate相同的话，才能保证undercharge和overcharge的钱数相同。

所以感觉B也对，虽然没有C表述得直接。请大家再帮我分析一下，thanx