The correct answer is D) Course 180°T when you cross the equator. This is because when a rhumb line course crosses the equator (latitude 0°), the rhumb line distance is the same as the great circle distance. This is because the curvature of the Earth is minimized at the equator, and the shortest distance between two points on the surface of the Earth is a straight line, which is the great circle. Therefore, the rhumb line, which is a line of constant bearing, coincides with the great circle at the equator. The other options are incorrect because A) in high latitudes, the rhumb line and great circle can differ significantly, and B) in low latitudes, the rhumb line is still not the same as the great circle. C) is also incorrect, as the rhumb line distance can be either longer or shorter than the great circle distance, depending on the course and location.