Hardly____we____to the station when the train arrived.(go)

had,gone
倒装据

could go,Hardly提前，用倒装句。

hardly can we go to the stadion when the train arrived.
否定词开头要求后面的句子倒装

had, gone

could 。。。go

从句过去时，主句用could

had, gone 倒装