You are the Security Consultant advising a company on security methods. This is a highly secure location that deals with sensitive national defense related data. They are very concerned about physical security as they had a breach last month. In that breach an individual had simply grabbed a laptop and ran out of the building. Which one of the following would have been most effective in preventing this? 

Answer options:

A. Not using laptops.
B. Keeping all doors locked with a guard.
C. Using a man-trap.
D. A sign in log.

C