The correct answer is (b). The astrolabe is an astronomical instrument used to determine the altitude of a celestial body above the horizon. It was formerly used by sailors to navigate by measuring the angle between the horizon and the stars. The astrolabe can also be used to determine the time of day, the latitude, and the longitude.
(a) Latitude and longitude are two coordinates that are used to specify the location of a point on Earth’s surface. Latitude is the angular distance north or south of the Equator, and longitude is the angular distance east or west of the Prime Meridian.
(c) The size of the Earth is the distance from the center of the Earth to its surface. The Earth is not a perfect sphere, but is slightly flattened at the poles. The equatorial diameter of the Earth is 12,756 km, and the polar diameter is 12,714 km.
(d) The depth of the sea is the distance from the surface of the sea to the bottom of the sea. The average depth of the sea is 3,794 meters.