Which part of the sailboat helps to determine its direction by interacting with wind?

The sails on a sailboat play a crucial role in determining its direction by interacting with the wind. Sails are designed to capture wind in order to generate propulsion. When wind flows over the sails, it creates differences in pressure on opposite sides, which pushes the boat forward. The angle and trim of the sails can be adjusted to optimize their effectiveness based on the prevailing wind conditions. This interaction enables the boat to move forward and turn in different directions, making the sails essential for navigation and control.

In contrast, while the keel and rudder are important for stability and steering, they do not directly interact with the wind to generate movement. The deck is simply the surface where people stand and work while sailing and does not have a role in influencing the sailboat’s direction through wind interaction. Thus, sails are the primary components that determine a sailboat's direction through their relationship with the wind.