例句：
You should make a copy of the disk as a backup.
你應(yīng)該將磁盤復(fù)制一個備份。
The police had backup from the army.
警方得到了軍方的增援。
Every part of the system has a backup.
這套系統(tǒng)的每個部分都有備件。
Sharon also sang backup for Barry Manilow.
莎倫還為巴里·馬尼洛唱了伴唱。
We can use him as a backup if one of the other players drops out.
如果有參賽者退出，我們可以用他作為替補(bǔ)。