单选题 Government department head: We already have a code of ethics that companies doing business with the department are urged to abide by. The fact that virtually all of the companies have agreed to abide by it indicates that it is successful. Therefore, neither stronger ethics regulations nor enforcement mechanisms are necessary to ensure ethical behavior by companies doing business with the department.
Which of the following, if true, casts most doubt on the department head's conclusion?

A、 The code of ethics applies only to companies that do business with the department.
B、 The code of ethics was instituted only after it was discovered that several companies had committed serious violations of ethics in their business with the department.
C、 A government investigation found that most of the companies that agreed to abide by the department's code of ethics are not complying with it.
D、 A survey of major companies found that several companies stopped doing business with the department because they did not want to agree to abide by the code of ethics.
E、 (E) A study of codes of ethics for companies found that the codes are most effective when the top executives of companies that agree to abide by them are fully committed to following them.

【正确答案】 C

【答案解析】