what must i do?

what must i do? what must I do正确吗 What I must do is study hard. What I must do ,what should I do ,what I can do ,I need the You must do exactly what I tell you to do what must do 与 what must I do 可以交换吗? what "must"i/we/you/he/she/they do and what "must not'' i/we how must i do和what must i do有什么区别 what must he do? what do I must Mr.Smith? 连词成句!急! What must I do _________the book.[open]怎么做 what must i do和what should i do 有什么区别