Question 1619Navigation General

The correct answer is C) zenith, nadir and the east point of the horizon. The prime vertical is the great circle on the celestial sphere that passes through the zenith, nadir, and the east point of the horizon. This is because the prime vertical is defined as the vertical circle that passes through the east and west points of the horizon. The other options are incorrect because they do not accurately describe the definition of the prime vertical. Option A refers to a celestial body, which is not part of the definition. Option B refers to the celestial poles, which are not the defining points of the prime vertical. Option D refers to the zenith and celestial poles, which is also not the correct definition.