why does seven afraid of nine?

why does seven afraid of nine? why is nine afraid of seven 猜谜：Why is nine afraid seven? 求几则英文谜语比如Why is Seven afraid of Nine ?Because seven eight(at why is nine afraid of seven?拜托各位了 3Q Why is six afraid of seven? why is ten afraid of seven? 10为什么怕7 why is ten afraid of seven 脑筋急转弯 Why is six afraid of seven?I am a kind of fruit,green Why are grils afraid of the letter Why are girls afraid of letter C why are dogs afraid of sunshine