can be表猜测 must be表肯定
把我的笔记弄下来给你看看好了.
例子:-Look!The man over there is wearing a red shirt the same as Lee.
-he can be Lee.I think.
-Look!The man over there is wearing a red shirt the same as Lee.I think only Lee has such a stupid shirt.
-He must be Lee.
例子2:can't be是must be 的否定
-Look!The man over there is wearing a red shirt the same as Lee.
-he can't be Lee.He went to Shanghai yesterday.