I think he must be mad.有语法错误吗?

I think he must be a fool.这句话有语法错误吗 I think she must be over forty.有语法错误吗 I think you must be a pretty girl ,don't you?有语法错误吗? he must be either mad or drunk that he said so must be quite encouraging,i think _____ he said so must be quite inspiring,I think. I think he must be in the office now,______? I think he must be at home now变反意疑问句 i think he must be right的反义疑问句? I think he must be a teacher,_____ _____. I don't think he must be sleepy, _______? that must would be nice有语法错误吗,