________hedrivenmorecarefully,theaccidentwouldnothavehappenedtheotherday.
A.BeB.HadC.HasD.Would have在线课程B
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。