How does the mechanical advantage of a screw increase?

The mechanical advantage of a screw increases when you increase the number of threads or decrease the pitch. The pitch of a screw refers to the distance between adjacent threads. A screw with a smaller pitch has threads that are closer together, which means that for every complete turn of the screw, it moves a shorter distance into the material. This allows more mechanical advantage because the effort needed to turn the screw translates to a greater force exerted on the load being lifted.

When the number of threads increases or the pitch decreases, you effectively create more leverage. This means that for a given amount of rotational input (turning the screw), you are able to move a load further with less force. The closer spacing of the threads allows the screw to apply a larger output force over a shorter distance instead of requiring a large amount of force to lift a larger load over a longer distance. Hence, option C accurately describes how mechanical advantage is enhanced in a screw mechanism.