If the captain had been more careful,he could have prevented the accident.提问!
问题描述：
If the captain had been more careful,he could have prevented the accident.提问!
If the captain had been more careful,he could have prevented the accident.
这句的后半句,有情态动词和现在完成时,有这种表述么?
不是手情态动词后面的动词用圆形么?为啥还能有时态的的变化?
答
对过去发生的事情作出与事实相反的推论,条件句用had + -ed,主句用should/ could /would have + -ed.
should/ could /would have + -ed可以表示“本来可以.,但是不是那样发生的,与事实相反;或者：“应该/可能已经...”,表示推测,不一定与事实不符.
所谓动词原形或者不定式,其实也有多种形式：do (不能用did,does）； have done （不能用had,has）；be done （被动）； be doing进行（当然不能用am ,is are,was ,were); have been doing (完成进行)