he driven more carefully, the accident would not have happened the other day.
A. Be
B. Had
C. Has
D. Would have
网友回答
A. Be
(答案→)B. Had
C. Has
D. Would have
解析：考查虚拟语气。“如果他开车在小心一点，事故就不会发生了。”根据主句的would not have happened可知，与过去相反，故用过去完成时，即If he had driven...，If引导的虚拟语气常用省略形式，把had提前，即Had he driven...。故选B。