Which simple machine transfers force along a curved path?

The correct choice is the pulley, as it effectively transfers force along a curved path, particularly when using a system of ropes or cables. When a rope is looped over a wheel, any force applied to one end of the rope is directed around the curvature of the wheel, changing the direction of the force applied. This allows for lifting or moving loads in a different direction than the applied force, utilizing the smooth curvature of the wheel to reduce friction and facilitate motion.

In contrast, inclined planes function by providing a sloped surface that allows for lifting heavy objects by distributing their weight along a longer distance. While they do assist in moving objects upward, they do not transfer forces along a path defined by curvature.

Levers operate by pivoting around a fulcrum and do not involve any curved pathways; rather, they produce mechanical advantage through leverage. Similarly, the wheel and axle, although they rotate, primarily serve to provide circular motion rather than transferring force along a curved path like a pulley does.

The effectiveness of pulleys in changing the direction of force while following a curved path is what sets them apart from the other simple machines.