Except the door key, what can be done to the server network security for entrance purposes?

Except the door key, what can be done to the server network security for entrance purposes?

A.
Locks on the server chassis

B.
Locks on the server rack

C.
Entrance passwords to enter the server room

D.
Installed server security software

Explanation:
The first introduction to server network security for most employees occurs at the entrance to the server room.
Incorrect Answers:
A, B, C: Yes, all this is security measures, but it does not keep them from entering the server room.
References:
Charles J. Brooks, Server+ Certification Exam Cram 2 (Exam SK0-002), QUE Publishing, Indianapolis, 2006, p. 464.