Which of the following security controls might force an operator into collusion with personnel assigned...

The questions specifically said: "within a different function" which eliminate Job Rotation as a choice.

Management monitoring of audit logs is a detective control and it would not prevent collusion.

Changing passwords regularly would not prevent such attack.

This question validates if you understand the concept of separation of duties and least privilege. By having operators that have only the minimum access level they need and only what they need to do their duties within a company, the operations personnel would be force to use collusion to defeat those security mechanism.

Source: TIPTON, Hal, (ISC)2, Introduction to the CISSP Exam presentation.