What simple machine is frequently used to split objects apart?

The correct choice is the wedge, which is a simple machine designed to split or separate objects apart. A wedge works by converting a force applied to its blunt end into an outward force on the sides, effectively driving itself into the material and causing it to split. An everyday example of a wedge is a knife or an axe, both of which are used to cut through various materials.

In terms of the other options, a screw converts rotational motion into linear motion and is primarily used for fastening objects together rather than splitting them. A pulley changes the direction of a force and is used to lift objects, and an inclined plane reduces the effort needed to lift objects but does not inherently split them. Thus, while all these machines serve important purposes in mechanics, the wedge specifically excels in the role of splitting or separating materials.