If I had been a little more careful I the wallet behind.A. won't leaveB. hadn't leftC. d

问题补充：

If I had been a little more careful, I the wallet behind.

A. won leave

B. hadn left

C. didn leave

D. wouldn have left

答案：

A. won leave

B. hadn left

C. didn leave

(答案→)D. wouldn have left

解析：句意：如果我能小心一些，我就不会丢下钱包了。If条件句用了had done，说明是和过去相反的虚拟语气，主句用would have done表示对过去情况的虚拟，所以选D。