The correct answer is “control evaluator & consultant”. During any system development or acquisition, the security staff should evaluate security controls and advise (or consult) on the strengths and weaknesses with those responsible for making the final decisions on the project.
The other answers are not correct because:
policeman -It is never a good idea for the security staff to be placed into this type of role (though it is sometimes unavoidable). During system development or acquisition, there should be no need of anyone filling the role of policeman.
data owner -In this case, the data owner would be the person asking for the new system to manage, control, and secure information they are responsible for. While it is possible the security staff could also be the data owner for such a project if they happen to have responsibility for the information, it is also possible someone else would fill this role. Therefore, the best answer remains “control evaluator & consultant”.
application user -Again, it is possible this could be the security staff, but it could also be many other people or groups. So this is not the best answer.
Reference: Official ISC2 Guide page: 555 -560 All in One Third Edition page: 832 -846