The correct answer is B) Declination. In the celestial equator system of coordinates, declination is the celestial equivalent to latitude on the terrestrial sphere. Just as latitude measures the north-south position of a point on the Earth's surface, declination measures the north-south position of a celestial body on the celestial sphere. Declination is measured in degrees north or south of the celestial equator, similar to how latitude is measured north or south of the Earth's equator. The other options are incorrect because they represent different celestial coordinate system components - celestial meridians are great circles passing through the celestial poles, right ascension is the east-west coordinate, and altitude is the vertical angle of a celestial body above the horizon.