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。