介词 by和acrossIf you really have to leave during the meeting,you had better leave _______ the back door.为什么不用across?

问题描述:

介词 by和across
If you really have to leave during the meeting,you had better leave _______ the back door.
为什么不用across?

by 在这里相当于“经过”=via
across是从平面上方穿过“横穿”