这个好解决,例如 There isn't any difference between the two .I really don't known which to choose这就是一个非谓语动词 疑问词带不定时的结构,实际上我们要把I really don't known which to choose不定时看成是宾语成分 I 是主语 really don't known 是谓语 which to choose是宾语