Answer:
A mantrap
Explanation:
A mantrap controls access to a secure area, and only allows one person to pass at a time. The scenario describes the social engineering tactic of tailgating, not the control to prevent it.
Some advanced mantraps include identification and authorization systems, such as biometric systems or smart cards and PINs. However, biometrics and smart cards used for physical security do not restrict passage to one person at a time unless they are combined with a mantrap.
