How do people find their ways？ At first， people did it by looking at the sun， the moon and stars， Later， we started to use the compass（指南针）．Today， there are navigation satellite systems．

    A navigation satellite system uses groups of satellites， They send information to a receiver， such as your smart phone． Then they can find where you are．

    The earliest navigation system is the Global （全球的） Positioning System（GPS） of the United States， The US has put 24 satellites into space to make sure GPS can locate a person correctly and globally． Russia's GLONASS and European Union's Galileo can also work globally．

    The BeiDou Navigation Satellite System （BDS）is China's homegrown navigation system． It was set up in 2000． With it， China became the third country to build a navigation system after the US and Russia．

    BeiDou can find you wherever you are． It helps you go faster by finding shortcuts and using correct directions． When you are in trouble and call the police， they will know exactly where you are if you have a smart phone that uses BeiDou．

    Today， there are more than 20 BeiDou satellites above our heads． And the system is able to offer open services to the Asia﹣ Pacific area．

    China plans to send more BeiDou 3 satellites into space． BeiDou﹣3's position accuracy（精确度） is less than five meters， By 2020， the BeiDou system will have 35 satellites and begin serving Globally．

（1）How did people find their ways at first according to this passage？　　

A． By looking at the sun， the moon and stars．

B． By using the navigation satellite systems．

C． By looking at the compass．

（2）How many navigation satellite systems are mentioned in the passage？　　

A． Two．

B． Three．

C． Four．

（3）What does the underlined word"locate "in the third paragraph mean？　　

A．位于

B．设置

C．定位

（4）What do you know about the BeiDou system？　　

A．It was set up before GPS．

B．It will begin serving globally by 2020．

C． There are less than 20 BeiDou satellites today．