V. Read the following passage and choose the best answer to fill in each blank.

The USA invented the Global Positioning System (GPS) in the 1970s. ___(1)___, it was a military project, but now anyone can use the system to find out exactly their locations and track their movements. For GPS to ___(2)___, your receiver (or smartphone) must be in contact with four or more satellites in space. Then it uses the data to calculate the ___(3)___ time and position on Earth. However, it is not enough for survival situations (escaping the jungles or deserts) because you ___(4)___ know your direction (which way you are moving) and your speed (how fast you are moving). GPS provides this information, by tracking your position over time. For modern explorers, a smartphone and GPS are ___(5)___ as a compass, torch and map. With the right applications, your smartphone will help you survive.