在反意疑问句中:nor did I和so did I的区别和用法

问题描述:

在反意疑问句中:nor did I和so did I的区别和用法
----I stayed up late last night for the exam
----_______.
A.So did I
B.Nor did I
我知道答案是B,但为什么不能选A

前一个是别人说“他不怎么怎么样”时,你和他一样,就nor did I.(nor表示否定)
后一个是别人说“他怎么怎么样”时,你和他一样,就so did I.(so表示肯定)
如:I did not go to America before.Nor did I.
I went to America before.So did I.