Since Charlie's control line is attached to the model airplane, and the airplane travels an arc of 120 feet from point B to point C, we can determine the length of the control line using this information.
A control line in this context is essentially the radius of the circular path traveled by the airplane. Given the arc length of 120 feet, the radius (or length of the control line) would correspond to this distance since the arc length of a circle is directly proportional to the radius when considering the angular measurement.
Therefore, the control line is about 120 feet long.
