The prime vertical passes through A. The east point of the horizon B. The west point of the horizon C. The zenith point of the observer D. All the above

The prime vertical is the vertical circle that passes through the zenith and the east and west points of the horizon. It is the great circle that divides the celestial sphere into two hemispheres, the eastern and western hemispheres.

The east point of the horizon is the point on the horizon where the sun rises at sunrise. The west point of the horizon is the point on the horizon where the sun sets at sunset. The zenith is the point directly overhead.

Therefore, the correct answer is D. All of the above.