If they had starded earlier than expected,they would be here now.这是虚拟语气中的混合条件句.即,主句和从句假设的时间不一致.本句的从句假设时间是过去时,主句的假设时间是一般现在时.那if my lawyer had been here last saturday ,he would have prevented me from going 怎么不用would preventIf my lawyer had been here last saturday ,he would have prevented me from going. 从句假设的时间是星期六（过去时），当然是星期六在这里的时候阻止了，所以主句也是过去时啦。would have prevented 算过去将来完成时？不是过去将来完成时，这是虚拟语气的条件句中主句谓语动词的形式，表示与过去时间相反的假设。