我的世界you must be logged in to do that我输过了注册和登陆

我的世界you must be logged in to do that我输过了注册和登陆 You must be strong . you must be You must be hungry You must be joking You must be confident. You must be dreaming you must be careful YOU MUST BE A LOVELY GIRL.谁帮我解释一下这句话的意思. 关于must be,will be的正确用法像是will be,must be这种带be动词原形的后面加的是什么词性?我见过 you must be beautiful.这种用法,但是如果我在后面加动词 you must be to do your homework.这样是正确的吗?希望 you must be ___!(kid) You must be carful next You must be happy oh., you must be joking,救命 You Must Be Strong 歌词 You must certainly be happy i must be cull you you must be mistaken是什么意思?