单选题 I have told my friend that if I had known he was in hot water, I would go and help him out.
A. knew B. was knowing
C. should know D. will know

【正确答案】 A
【答案解析】此句也为虚拟句。当主句用了would do的动词形式，条件句的动词应以一般过去时的形式出现。