1. 答案：C.
2. 解释：
1）Had I known it = If I had known it
这是if引导的条件状语从句使用虚拟语气时常常考查的倒装语法.
2）如果if从句中出现了were/should/had的话,可以把这三个词提前至从句句首,并且把if省略.
如：If I were you, I would say no to him.
= Were I you, I would say no to him.
If you were to leave tomorrow, I would not visit your family.
= Were you to leave tomorrow, I would not visit your family.
If you should leave tomorrow, I would not visit your family.
= Should you leave tomorrow, I would not visit your family.
3）最后需要提醒你的是,如果if从句出现not否定时,则not不能与上述三词一起提前.
如：If he hadn't taken your advice, he would succeed now.
= Had he not taken your advice, he would succeed now.
而变成：Had not he taken your advice, he would succeed now.或Hadn't he taken your advice, he would succeed now的话,都是错误的. 原创回答团（第159号会员）