The answer is (a): the air track glider will move to the right, as seen in an mpeg video by clicking your mouse on the photograph at the left below. Note that after the video begins you hear start of the air track blower then the start of the air gun blowing the "wind" into the sail.
When the air stream deflects off the sail, it sets exerts a force vector as seen in the diagram at the right above. Because the glider can only move along the air track, the component to the right in the diagram causes the glider to move to the right.
This is the situation that allows a sailor to "tack," or sail with a component of motion against the wind.