当陈述部分的主语有this,that,everything,something,nothing等词时,疑问句部分的主语用it,如果主语部分有these,those, 要用they.
eg:That is nice, isn't it?
These books are of great benefit, aren't they?
当陈述部分的主语是everyonr,someone,anyone,everybody,somebody,nobody,no one 等不定代词时,反意疑问句的主语通常用they, 有时也用he.
eg:Everyone likes you, don't they?
希望对你有帮助.