Have you ever counted the number of digits（数字） in your mobile phone number？Your number has 1 1 digits.You may sometimes find it hard to remember your number.That's because China has the longest mobile phone numbers in the world.Why is that？
    The 1 1 digits can be divided into three parts.Each part has a different meaning.The first three numbers tell you which mobile phone service provider you are using.For example，135 is for China Mobile Communications Corporation and 188 is for China Unicom.The fourth to the seventh digits tell you where the number is registered（注册）.And the last four digits are random （随机的）.
    The main reason for using 1 1 digits is that we have the largest population in the world.We once had 10 numbers.But as our population grew，there were not enough numbers for us to use.So we began to use 1 1 digits starting from 1999.Eleven digits can be used to make tens of billions of mobile phone numbers.That's enough for each person to have seven or eight phone numbers to use in China.
    Besides China，Britain and Japan also use 11-digit mobile phone numbers.But their numbers always start with O.So they cannot create as many numbers as we can.Countries like the United States，Australia and India use phone numbers with 10 digits.Canada's mobile phone numbers are perhaps the shortest in the world：they use seven digits.

根据短文内容回答下列问题。
（1）How many parts can Chinese mobile phone numbers be divided into？

Three.

Three.

（2）What can we know from the fourth to the seventh digits of a mobile phone number in China？

We can know where the number is registered.

We can know where the number is registered.

（3）Why does China use 1 1 digits for mobile phone numbers？

Because we have the largest population in the world.

Because we have the largest population in the world.

（4）Is China the only country that uses 11-digit mobile phone numbers in the world？

No，it isn't.

No，it isn't.

（5）Which country perhaps has the shortest mobile phone numbers in the world？

Canada.

Canada.