为什么where were you last night 句子里用的是were ?

问题描述:

为什么where were you last night 句子里用的是were ?
you 不是单数吗
可以用was 吗 where was you last night.这样
请说明一下为什么

you是第二人称“你”,第二人称与be动词连用时都用be动词的复数形式.
eg.You are a beautiful girl.
Were you happy last night?