加拿大的手机号码可能是世界上最短的：他们使用7位数字。
Canada's mobile phone numbers are perhaps the shortest in the world: they use seven digits.
在中国，我们能从手机号码的第四位数到第七位数知道些什么？
What can we know from the fourth to the seventh digits of a mobile phone number in China?
加拿大的手机号码可能是世界上最短的：使用7位数字。
Canada's mobile phone numbers are perhaps the world's shortest: they use seven digits.
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