when did you bring it to us
问题描述：
when did you bring it to us
为什么用did
不用were?
when were you brought it to us
答
A brings something to B 表示A给B带来了某物.
它用when的问句就是when does A bring something to
（A什么时候给B带某物来?）
如果用were,应该是Something were brought to B,是被动语气,表示某物被带来给B.
在这句话,如果填Were表被动,至少应该是When were it brought to us?（它什么时候被带来给我们?）或者When were you brought to us?（你什么时候被带来给我们?——语法对,句意不通）.但后面有了it,说明这句话不是被动,所以要填主动的did.