Which of the following is the MOST effective control over visitor access to a data center?

A.
Visitors are escorted.

B.
Visitor badges are required.

C.
Visitors sign in.

D.
Visitors are spot-checked by operators.

Explanation:
Escorting visitors will provide the best assurance that visitors have permission to access the data processing facility. Choices B and C are not reliable controls. Choice D is incorrect because visitors should be accompanied at all times while they are on the premises, not only when they are in the data processing facility.