The correct answer is C, Bollards. Bollards are physical security controls designed to prevent vehicles from entering restricted areas or crashing into buildings, entrances, sensitive facilities, or pedestrian zones. They are commonly installed outside government buildings, data centers, banks, airports, and other critical infrastructure locations to mitigate vehicle-borne threats and unauthorized vehicle access. Depending on the security requirement, bollards may be fixed, removable, retractable, or reinforced to withstand high-impact collisions.

In CEH physical security concepts, organizations use preventive physical controls to protect personnel, equipment, and facilities from unauthorized access and physical attacks. Bollards are considered perimeter security controls because they create a physical barrier between vehicles and protected assets. A receptionist provides administrative access control but cannot physically stop a vehicle. A mantrap is an access-control vestibule used to restrict and verify personnel entry. A turnstile controls pedestrian movement and helps prevent tailgating. Since the question specifically asks about stopping vehicles from crashing through building doors, bollards are the most appropriate and effective security feature.

Answer: C