Question

what type of hardware is used to prevent gears and pulleys from spinning on a shaft?
a key
blind nut
a collar pin
a retaining ring

Explanation:

A key is a common mechanical component used to prevent relative rotation between a shaft and a gear or pulley mounted on it. Blind rivets are for joining materials, cotter pins are for preventing axial movement, and retaining rings are for axial location.

Answer:

A. a key