Final answer:
The most common form of physical access control is keys and locks due to their simplicity and reliability in securing properties and preventing unauthorized access.
Step-by-step explanation:
The most common form of physical access control is keys and locks. While technology has introduced more sophisticated methods such as electromagnetic locks, FOB access, and swipe card systems, traditional keys and locks remain widely used due to their simplicity, cost-effectiveness, and reliability. Despite being low-tech, keys and locks are the primary safeguard for securing doors and preventing unauthorized access in a vast number of settings, from residential to commercial properties.