Which components should not be relied upon for the mechanical means of the extinguishing system?

The correct answer focuses on the importance of the reliability and function of components in a dry chemical extinguishing system. Hardware components that are common to automatic functions may not be dependable in all situations, particularly in the context of a fire emergency. This is because these components are often designed with specific functions that can sometimes fail due to various reasons such as mechanical wear, environmental factors, or human error during maintenance.

In contrast, the other choices, such as electrical components, backup power systems, and manual engagement tools, play critical roles in ensuring the system operates effectively during a fire. Electrical components can trigger the system, backup power systems ensure functionality during power outages, and manual engagement tools allow for immediate activation by personnel. Therefore, relying solely on hardware components that are integral to the automatic functionality may compromise the effectiveness and responsiveness of the extinguishing system in an emergency.