I have told my friend that if I_______ he was in hot water, i would go and help him out.
A: knew B: had known C:should know D:will know
您认为答案选什么？为什么？
书上的答案是选择A，说因为主句使用：would do something,故从句使用过去时间。
我最初也是选择B,但是转念一想，如果用had done, 主句是不是就应该用would have done了？不得其解，等待与大家继续探讨……