在职攻硕英语考试

根据网考网考试中心的统计分析，以下试题在2019/11/14日在职攻硕英语习题练习中，答错率较高，为：99%
【单选题】It could have saved me some trouble ______ about it.
A．had I known
B．I had known
C．did I know
D．I knew