先感谢愿意回答的各位强者，帮同学代问：
题目: If we _____ (to take) MRT, we could arrive here earlier.
同学直觉的答案是 took，正确填空答案也是 took ，但是同学同时也非常疑惑为何不能用 had taken ，因为与过去事实相反不是吗？为了这个问题她折腾我一晚上，我也答不上来.....
恳请各位帮忙。

如果条件副词子句要用完成式，主要句子也要用完成式变could have arrived

赞同楼上应该是过去相反