What should you use to determine true course when crossing numerous meridians on a cross-country flight?

To determine the true course when crossing numerous meridians during a cross-country flight, the most effective method is to use the meridian closest to the center of your course. This approach enables you to get an accurate reference point that reflects the general direction of your flight path, as it minimizes the angular difference that could occur if you were to reference a more distant meridian.

Using the meridian closest to the center offers a practical balance between the effects of distortion due to the curvature of the Earth and the varying distances involved. This method helps pilots maintain a consistent and accurate heading, which is essential, especially on longer flights where piloting precision is critical.

Other options like the farthest east meridian, the nearest checkpoint, or the prime meridian may not provide as reliable a reference for determining the true course, as they could introduce unnecessary complexity or inaccuracies in navigation when aligning with multiple meridian crossings.