You didn’t let me drive. If we ______ in turn, you ______ so

B

考查虚拟语气。句意：你让我开。如果我们轮流开车，你也不会变的如此累。因为与过去时相反，if引导的从句应用过去完成时，

时间
从句谓语形式
主句谓语形式


将来
动词过去式(be用were)
should + 动词原形
were to + 动词原形

would / should / might / could + 动词原形

现在
动词过去式(be 用 were)
would / should / might / could + 动词原形

过去
had +动词过去分词
would / should / might / could have + 动词过去分词
故选B。