Final answer:
The safe distance between an aggressor and a Security Guard should generally be five feet or more to ensure both reactivity and safety.
Step-by-step explanation:
The correct safe distance that should be maintained between an aggressor and a Security Guard is generally five feet or more. This distance is considered safe because it allows the security guard enough space to react effectively if the aggressor were to become a threat. This concept is similar to judging safe distances in other contexts, such as determining a safe distance from moving vehicles. For example, when crossing a street, one should estimate the safety based on how far away a car is, often in terms of car-lengths, before deciding it is safe to cross. Keeping a safe distance helps prevent unforeseen incidents and ensures safety for everyone involved.