Correct Answer:
C. Prevent tailgating
A "mantrap" is primarily used to Prevent tailgating. A mantrap, also known as an access control vestibule or airlock, is a small, secure area with two doors where only one door can be opened at a time. This design ensures that only one authorized person can enter at a time, preventing unauthorized individuals from following closely behind.
- While it enhances security, its primary function isn't to 'Catch intruders automatically' in the sense of an alarm, but to control entry.
- It does not directly 'Alert police' but rather restricts access.
- Therefore, 'None of these' is incorrect as preventing tailgating is its core function.