题目内容：

everybody knows the answer.(反意问句）
急

优质解答

如果陈述部分的主语为everyone,someone,no one等不定代词,其疑问部分的主语可以用he,也可以用they,因而疑问部分的谓语动词也可用复数形式.例如：
Everyone knows their job,don't they?
Everyone knows his job,doesn't he?
所以你的问题don't they/doesn't he都可以.