你会正确使用虚拟语气的倒装形式吗
请看典型考题：
__________ your address，I would have written to you.
A. Did I know B. Were I to know
C. Had I known D. If I should know
此题应选 C。这是虚拟语气的倒装形式。当虚拟条件句中含有 were，had，should，could等动词时，可以将if省略，然后将 were，had，should，could 等词移至句首：
1. If he should fail，he would kill himself.
→Should he fail，he would kill himself.
万一失败，他就会自杀。
2. If I were you，I would do it at once.
→Were I you，I would do it at once.
假若我是你，我就会马上做。
3. If I could do it，I would.
→Could I do it，I would.
要是我能做此事，我一定会做。
4. If he had seen you yesterday，he would haveasked you about it.
→Had he seen you yesterday，he would haveasked you about it.
他昨天要是看到了你，他就会问你这事了。
顺便说一句，以上移至句首的 had不一定是助动词，如果是实义动词也可倒装：
If he had money，he would buy a car.
→Had he money，he would buy a car.
他要是有钱，他就会买一辆小车