给你例句：
You must have read the book.你一定读过这本书
You must read the book.你一定要读这本书
You must have shown up in today's meeting. 今天的会议你一定出席了.
You must show up in today's meeting. 今天的会议你一定要出席.
must do的意思是必须做某事
must have done是对过去已有的事实做肯定的猜测