can,what,how,do,等,在句首到底怎么用,怎么区别`

can,what,how,do 这些词都一样放句首都是疑问句式。句式结构都是诸如Can I help you?can指能,可以。What Can i do for you?what指什么。How are you?How;指怎么样。。可以接how long,how often,有点表示量。。Do you drink?你会喝酒吗。Do是对助动词提问是用的。。。没实际意义