both the girl and her dog that were 英语问题

both the girl and her dog that were crossing the street were hit by a car.为什么这里要用were crossing而不能用crossed呢

用"were crossing"表示正在过街。这句话可以简化成both the gril and her dog crossing the street were hit by a car，同样表示正在过街。
和crossed的不同之处在于，当在这里用crossed the street，意思就是已经过了街，被撞了。

选d 当主语含有人跟物件或人跟动物的时候，要选that，因为主语不是只有一个

过去进行时表示动作持续的过程，即“在穿越马路的时候”被车撞了，而crossed则表示动作的完成，并不是“穿过马路”，然后被车撞了。