问题补充:
your advice, I would have had no trouble with my papers.
A. Had I followed
B. If I followed
C. If I have followed
D. Once I followed
答案:
(答案→)A. Had I followed
B. If I followed
C. If I have followed
D. Once I followed
解析:根据would have had可知, 这是是一个表示与过去事实相反的假设。if条件从句用过去完成时had done,又知if条件句中如有were, should, had,可以省去if,并使用倒装语序, 即were, should, had+主语+谓语动词。故答案为A。