Global Positioning Systems (全球定位系统) are now a part of everyday driving in many countries.These satellitebased systems provide turnbyturn directions to help people get to where they want to go.However，they can also cause a lot of problems，send you to the wrong place or leave you completely lost.Many times，the driver is to blame.Sometimes a GPS error is responsible.Most often，says Barry Brown，it is a combination of the two.
Barry Brown is with the Mobile Life Centre in Stockholm，Sweden.He told us about an incident involving a friend who had flown to an airport in the eastern United States.There he borrowed a GPSequipped car to use during his stay.Mr Brown says，“They just plugged in an address and then set off to their destination.And，then it wasn’t until they were driving for thirty minutes that they realized they actually put in a destination back on the West Coast where they lived.They actually put their home address in.So again，the GPS is kind of ‘garbage in garbage out’．”
Mr Brown says this is a common human error，but what makes the problem worse has to do with some of the shortcomings，or failures，of GPS equipment.He says，“One problem with a lot of the GPS units is they have a very small screen and they just tell you the next turn.Because they just give you the next turn，sometimes that means that it is not really giving you the overview that you would need to know that it’s going to the wrong place.”
Mr Brown says，“One of the things that struck us，perhaps the most important thing was that you have to know what you’re doing when you use a GPS.There are these new skills that people have developed.There are these new competencies (资格) that you need to have to be able to use a GPS because they sometimes go wrong.This goes against a common belief that GPS systems are for passive drivers who lack navigational skills.”
Barry Brown says to make GPS systems better we need a better understanding of how drivers，passengers and GPS systems work together.
According to Barry Brow，in most cases，________are blame for the problems.

A．human errors

B．GPS errors

C．errors caused by both drivers and GPS

D．errors caused by putting in a wrong address

The example of Barry Brown’s friend is used to show that________.

A．GPS is nothing but garbage

B．GPS is still not accurate enough

C．it is difficult for drivers to use GPS equipment

D．sometimes drivers are responsible for the problem

It can be inferred from the second paragraph that________.

A．it’s impossible to drive from the east to the west in the US

B．Barry Brown’s friend went to Stockholm，Sweden by plane

C．given wrong instructions，the GPS will produce wrong results

D．GPS systems are for passive drivers who lack navigational skills

Which of the followings is one of the shortcomings of GPS equipment?

A．It just tells the driver to turn once at a time.

B．It gives the driver the overview.

C．Its screen is too small to be seen clearly.

D．It is only suitable for passive drivers.

What’s the main idea of the text?

A．GPS systems are helpful for drivers.

B．Driving with GPS can be difficult to navigate (导航)．

C．Drivers should understand how GPS systems work.

D．Drivers should learn to use GPS systems correctly.