【题目】Sheldon could have defeated Howard in the match, but he _______ too careless at the last minute.
A. is B. was
C. has been D. had been
在线课程【答案】B
【解析】句意：Sheldon本可以在比赛中打败 Howard的，但是他最后一分钟太粗心了。前面的could have defeated是对过去情况的虚拟，but后面的内容是过去的事实，用一般过去式，所以选B。