--The mistake I had been more careful.---But you weren’t at that time.A. might have avoid

问题补充：

--The mistake, I had been more careful.

---But you weren’t at that time.

A. might have avoided

B. would avoid

C. would be avoided

D. might have been avoided

答案：

A. might have avoided

B. would avoid

C. would be avoided

D. might have been avoided

解析：句意：--如果我更加仔细一些，这个错误就会避免。--但是你当时没有。首先这个句子是个对过去情况的虚拟条件句，表示与过去事实相反的情况，if+主语+had done +其他+主语+should/would/could/might+have done+其他，所以排除BC，因为mistake和avoid是被动关系，所以选D。