答案：A

题目分析：句意：要是他明天离开，在星期五之前就会到那里。这里的were he to leave today="If" he were to leave today, 为虚拟语气，if条件句谓语中如果有系动词were，助动词should,had可将它提到主语前面，省去if.所以选A。