Which statement is true regarding the airplane's movement if the present heading is maintained?

When discussing the airplane's movement with respect to its current heading and the relationship to radials, option A is relevant as it pertains to the navigation concepts often used in flight planning and operations.

If the airplane’s present heading is maintained, and it is crossing the 180 radial at a 45° angle outbound, this indicates a specific relationship between the aircraft's path and the radial. A 45° angle outbound means that the airplane is traveling away from the station and is effectively leaving the 180 radial, which is oriented due south. This scenario typically occurs in navigation practices where the aircraft is transitioning from one radial to another, emphasizing the concept of intercepting navigation aids while maintaining a heading.

This understanding of how radials and airplane headings interact is essential for real-world navigation and ensures that pilots can effectively plot their courses while remaining aware of the aircraft's position relative to navigational aids.