Look what you have done!You should have been more careful.为什么一定要用should have been,老师和同学给的理由是都是过去时.可是如果用must be完全说得通啊,就是指现在对他说你要更仔细.
问题描述：
Look what you have done!You should have been more careful.为什么一定要用should have been,老师和同学给的理由是都是过去时.可是如果用must be完全说得通啊,就是指现在对他说你要更仔细.
答
should have been这叫虚拟语气,通常是由should或者would引起,时态是过去将来时.你本该更细心一些的（虚拟）,但是hi实际上没有足够细心（事实）,结果把事情办糟了.