How is the rudder on a sailboat primarily used?

The rudder on a sailboat is primarily used to steer the sailboat. It is a crucial component that allows the helmsman (the person steering the boat) to change the direction of the vessel by manipulating its position in the water. When the helmsman moves the tiller or wheel, it turns the rudder, which in turn alters the flow of water around the hull and creates a force that changes the boat's course.

This steering function is essential for navigating and maneuvering the sailboat safely, especially in various wind conditions and water traffic. Proper use of the rudder enhances a sailor's ability to control the boat's trajectory effectively, ensuring they can respond swiftly to changing circumstances on the water.

The other functions mentioned in the options, such as controlling the angle of the sails, stabilizing the boat, or raising and lowering the boom, involve different equipment and techniques that are necessary for sailing, but they do not pertain directly to the primary role of the rudder itself.