what type of hardware is used to prevent gears and pulleys from spinning on a shaft?\na key\nblind nut\na…

Brief Explanations:

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