Which of the following BEST characterizes a mantrap or deadman door, which is used as a deterrent control for the vulnerability of piggybacking?

A. A monitored double-doorway entry system

B. A monitored turnstile entry system

C. A monitored doorway entry system

D. A one-way door that does not allow exit after entry

Explanation:

A monitored double-doorway entry system, also referred to as a mantrap or deadman door, is used a deterrent control for the vulnerability of piggybacking.