Final answer:
A. Positive on/off switches. The appropriate switch for a belt sander is a positive on/off switch. This switch allows the user to turn the sander on and off by pressing a button or flipping a switch, and it stays in the desired position until manually switched off.
Step-by-step explanation:
The appropriate switch for a belt sander is a positive on/off switch, which is option A. This type of switch allows the user to turn the sander on and off by pressing a button or flipping a switch, and it stays in the desired position until manually switched off. This is ideal for belt sanders as it gives the user control over the operation of the tool.
Option B, momentary contact on/off switches, are switches that only work when pressure is applied and released. These switches are not suitable for belt sanders as the user would have to continuously apply and release pressure to keep the sander running.
Option C, constant pressure switch, is not a suitable switch for belt sanders either. This type of switch stays on as long as it is pressed and turns off when released. It is typically used in applications where continuous pressure is required to operate the tool, such as in some power tools.
Therefore, the correct answer is option A, positive on/off switches.