Establishing an Information Barrier department, one, following, employees

w1977

This is a question from Examwise Vol.2 Ethical and Professional Standard Q30. The answer is given in the book as B. However, I think this is incorrect. Can someone confirm?

Which one of the following requirements is least likely to help to ensure the establishment of an information barrier (fire wall)?

A: Physically separating departments and their files.
B: Monitor employees working for more than one department at any one time.
C: Limit proprietary trading when a firm has access to material nonpublic information.