Which of the following controls helps reduce the laser beam to below the MPE?

The answer focuses on the Beam Stop/Attenuator as the appropriate control measure to reduce the laser beam to below the Maximum Permissible Exposure (MPE). An attenuator is specifically designed to diminish the intensity of the laser beam to levels that are safe for human exposure. It functions by absorbing or dispersing part of the laser energy, thereby reducing the potential risk from accidental exposure.

In contrast, other controls such as an Interlock System, while they contribute to safety by preventing access to hazardous areas when lasers are active, do not directly reduce the laser beam's intensity. Warning Labels serve to notify individuals of the potential hazards associated with laser usage but do not alter or mitigate the actual laser beam itself. Protective Curtains can block or redirect the laser beam but may not effectively reduce the beam's intensity to below the MPE. Thus, the Beam Stop/Attenuator stands out as the most effective means of ensuring safety by addressing the beam's intensity directly.