Where on Earth are you? Navigators (导航员) use lines of latitu

Where on Earth are you? Navigators (导航员) use lines of latitude and lines of longitude to locate places. Lines of latitude run east and west around Earth. On a map or globe, these lines appear as running sideways or horizontally. Lines of longitude run north and south around Earth. These lines go up and down or vertically on a map or globe. These lines create an imaginary graph paper on the Earth. They make it possible to find an absolute, or exact, location on Earth. They even allow us to give an absolute location to a place out in the middle of the ocean.
Lines of latitude tell us how far north or south of the Equator we are. Sailors have used primitive navigation tools, like astrolabes, since ancient times. The astrolabe uses the sun and stars to find an approximate location. Using such tools, they have been able to approximate their distance from the equator. Although their instruments may not have been the high quality we have now, they were incredibly accurate (精确) for their time.
Lines of longitude tell us how far east or west of the prime meridian (本初子午线) we are. Sailors constantly looked for new ways to increase their navigation skills. Still, it wasn’t until the 18th century that they were able to measure degrees of longitude. They would have been very envious of the technology available to us today.
When we use lines of latitude and longitude together, we can get a very precise location. If we want to identify the absolute location of a point, we look where the latitude and longitude lines cross nearest to that point. We use the coordinates (坐标) for that point as its address. Many maps today include degrees of latitude and longitude.
小题1:______ make it possible for people to find an exact place on Earth.

A．Latitudes

B．Longitudes

C．Navigators

D．Sailors

小题2:The second paragraph mainly talks about _______.