Read the following passage and think of a word which best fits each space. Use only ONE word for each space.
Getting from place to place has been a challenge for humans (1) the beginning of man’s existence. Not only (2) people struggle with the actually physical problems of travel, but they also need to know the right direction to go. In one’s own little part of the world, this may have been relatively easy, but, as humans expanded further and further, it became necessary to determine how to get from one
place to (3) and back again. Paths, roads, and trails made journeys easier, and the creation of maps transmitted this knowledge to others. (4) , once humans pushed onto the vast oceans, there were (5) roads or accurate maps. The compass, showing the magnetic north, was a great, yet imperfect, aid. Latitude could be measured by sun angles, but (6) the perfection of timepieces in the 19th century, it was almost impossible to measure longitude. Fortunately, today there is a device which allows people easily to find their position no matter (7) they are: the Global Positioning System (GPS).
The Global Positioning System (8) of a series of twenty-four satellites in geosynchronous orbit around Earth at an altitude of 12,500 miles. These satellites are in fixed positions, so, by reading the
(9) from three of them, a person holding a GPS receiver can know exactly where he is. The GPS receiver synchronizes its clock with (10) of the satellites’ atomic clocks.