Final answer:
Increasing the radius of the handle of the screwdriver is the way to reduce the force required to turn a screw, as it increases the mechanical advantage by applying the force over a larger rotational distance.
Step-by-step explanation:
One way to reduce the force required to turn a screw when using a screwdriver, which is an example of a wheel and axle, a type of simple machine, is by increasing the radius of the handle (Option D). A screwdriver functions as a lever where the handle is the effort arm, and the axle is the pivot point. According to the principle of levers, increasing the length of the effort arm (handle) allows for a larger rotational distance over which the force is applied, thereby requiring less force to achieve the same amount of work.
Simple machines like the wheel and axle are designed to make work easier by either changing the magnitude of force or its direction. The mechanical advantage (MA) of a simple machine is the ratio of the output force to the input force, and in the case of a wheel and axle, increasing the radius of the handle effectively increases the MA and reduces the input force needed to turn the screw.