应该是用过去完成时, 因为在含有before的主从复合句中,一般在从句中使用一般过去时,主句中使用过去完成时.例如: Lily had written some letters before she went out shopping. 有时,也可以在从句中用过去完成时,主句中用一般过去时,这样就可使描述更为生动.试比较: We got to the station before the train had left.火车尚未开动之前,我们就到了车站. We had got to the station before the train left.火车开出之前,我们就已经到了车站.