How can mechanical advantage be achieved using pulleys?

Mechanical advantage in pulley systems is primarily achieved through the combination of fixed and movable pulleys. When a fixed pulley is used, it changes the direction of the force applied, making it easier to lift a load, but it does not reduce the amount of force needed. In contrast, a movable pulley allows for a portion of the weight to be distributed, effectively reducing the amount of input force required to lift a load.

When a fixed pulley is combined with a movable pulley, the system allows the user to lift heavier loads with less force. This combination results in an increased mechanical advantage because it effectively reduces the force needed to lift the load by increasing the number of segments of rope supporting the weight. Each segment of rope supports part of the load, which further decreases the force required to lift it.

This is why the combination of a fixed pulley with a movable pulley is the most effective way to achieve mechanical advantage in pulleys, making it the correct choice for the question.