Which of the following is a common duty of a security guard?

Monitoring surveillance equipment is a common duty of a security guard because it is a fundamental aspect of ensuring safety and security in a given environment. Security guards are often responsible for overseeing video feeds from surveillance cameras, detecting any suspicious behavior, and responding to incidents as they arise. This task allows them to maintain a vigilant presence, identify potential threats, and assist in the prevention of crimes or disturbances.

In contrast, writing policy for law enforcement, developing security training curriculum, and conducting criminal investigations are specialized tasks typically handled by law enforcement agencies, security management professionals, or experienced investigators. These responsibilities require a higher level of authority, specialized training, and a deep understanding of legal frameworks, which are beyond the typical scope of a security guard's role.