一、阅读原文
PASSAGE · 先通读全文，再逐空回看前后句P1Have you ever counted the number of digits (数位) in your mobile phone number? 1 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?
P22 Each part has a different meaning. The first three digits tell you which mobile phone service provider you are using. 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).
P3The main reason for using 11 digits is that we have the largest population in the world. 3 But as mobile phone users grew, there were not enough numbers for us to use. So we began to use 11 digits from 1999. Eleven digits can be used to create tens of billions of mobile phone numbers. 4
P4Besides China, Britain and Japan also use 11-digit mobile phone numbers. But their numbers always start with 0. 5 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 7 digits.