Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

What is GPS? The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites___ (131) into orbit by the U.S. Department of Defense. GPS was originally___ (132) for for military applications, but in the 1980s, the government made the system available for civilian use. GPS works in any weather conditions, anywhere in the world, 24 hours a day. There are no subscription fees or setup charges to use GPS. GPS satellites circle the Earth twice a day in a very precise orbit and transmit signal information to Earth. GPS receivers take this information and use triangulation to calculate the user's exact location. Essentially, the GPS receiver compares the time a signal was transmitted by a satellite with the time it was received.___ (133) tells the GPS receiver how far away the satellite is. Now, with distance measurements from a few more satellites, the receiver can determine the user's position and display it on the unit's electronic map. A GPS receiver must be locked on to the___ (134) of at least three satellites to calculate a 2D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been determined, the GPS unit ___(135), such as speed, track, trip distance, distance to destination, sunrise and sunset time and more.

The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of 24 satellites___ (131) into orbit by the U.S.