how you doing为什么用doing啊

how you doing为什么用doing啊 how you doing RT怎么用? How are you doing? How are you doing? How are you doing? how you doing How are you doing? how are you doing How are you doing these days?为什么用do的现在分词 how long have you been doing that为什么用现在完成进行时 为什么老友记中乔伊老是说how you doing,可是事实上不是应该是how are you doing?吗 how are you doing 还是how you doing? how are you ledies doing Hello,how are you doing? how are you doing对么 how are you doing翻译 翻译how are you doing? How did you doing spend your holiday?你假期怎么过的?我以为这句话应该是 How did you spend your holiday?但是为什么要加个doing 为什么要用强调啊？强调又是如何的用法呢？