Final answer:
The most common type of physical access control is locks and keys due to their simplicity and their foundational role in securing buildings and areas against unauthorized access.
Step-by-step explanation:
The most common type of physical access control is B. Locks and keys. They are widely used due to their simplicity and effectiveness. Other methods such as alarm codes, employee identification cards, and special visitor/contractor passes certainly play a role in access control, but locks and keys remain the foundational security measure for controlling physical access to buildings, offices, and other secure areas. Simple mechanical locks can prevent unauthorized entry and require no technical knowledge for users to operate with a physical key.