The mum effect can occur for all of the following reasons EXCEPT:

A) An employee's fear of retribution for bringing bad news.
B) An employee's unwillingness to identify personal mistakes.
C) An employee's general desire to please.
D) An employee's desire to be polite.
E) An employee's desire to speak out at meetings.

The mum effect refers to employees' reluctance to speak up about concerns or issues in the workplace. Option E suggests that the employee has a desire to speak out, which is not consistent with the mum effect. Therefore, it is the only option that is not a reason for the mum effect. The other options all suggest reasons why an employee might be hesitant to speak up, whether due to fear of retribution (A), unwillingness to identify mistakes (B), general desire to please (C), or desire to be polite (D).