Final answer:
True, the action is the central part of a pistol which includes mechanisms for loading, firing, and ejection of cartridges, with other parts attached to it.
Step-by-step explanation:
The statement that the action is the backbone to which all other parts of a pistol are attached is true. In the design of a pistol, the action refers to the mechanism that handles the loading, firing, and ejection of cartridges. This includes parts such as the trigger system, the firing pin, and the ejection and extraction mechanisms. The action is essentially the functional core of the firearm, and other components, such as the barrel, grips, and sights, are designed around it.