Explanation
A risk assessment would be most helpful to management in understanding at a very high level the threats, probabilities and existing controls. Developing a security architecture, installing a network intrusion detection system (NIDS) and preparing a list of attacks on the network and developing a network security policy would not be as effective in highlighting the importance to management and would follow only after performing a risk assessment.

Explanation
System users, specifically the user acceptance testers, would be in the best position to note whether new exposures are introduced during the change management process. The system designer or system analyst, data security officer and operations manager would not be as closely involved in testing code changes.