Have you ever counted the number of digits （數(shù)字） in your mobile phone number？Your number has 11 digits.You may sometimes find it hard to r（1）

emember

emember

your number.That's because China has the l（2）

ongest

ongest

mobile phone number in the world.Why is that？
   The 11 digits can be divided into three parts.Each part has a different m（3）

eaning

eaning

.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 f（4）

ourth

ourth

to the seventh digits tell you where the number is registered （注冊(cè)）.And the last four digits are random （隨機(jī)的）.
   The main r（5）

eason

eason

for using 11 digits is that we have the largest population in the world.We once had 10 numbers.But as our population g（6）

rew

rew

，there were not enough numbers for us to use.So we began to use 11 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.
   And mobile phone numbers can be r（7）

ecycled

ecycled

.Usually，the service provider will reuse a canceled（注銷的） number after three to six months.If you call a number that you haven't contacted for a long time，you may find that its o（8）

wner

wner

has changed.
   Besides China，Britain and Japan also use 11-digit mobile phone numbers.B（9）

ut

ut

their numbers always start with 0.So they cannot create as many numbers as we can.C（10）

ountries

ountries

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.