英语句子结构如果是“主句+ 时间状语从句”的话,一般遵循“主将从现”原则,即主句是一般将来时,从句用一般现在时; 主句是过去将来时,从句用一般过去时.如：
1.I shall wait here until he comes back.
2.He said he would not go back home unitl I gave him a promise.