b开头p结尾的单词

　　例句：

　　You should make a copy of the disk as a backup.

　　你应该将磁盘复制一个备份。

　　The police had backup from the army.

　　警方得到了军方的增援。

　　Every part of the system has a backup.

　　这套系统的每个部分都有备件。

　　Sharon also sang backup for Barry Manilow.

　　莎伦还为巴里·马尼洛唱了伴唱。

　　We can use him as a backup if one of the other players drops out.

　　如果有参赛者退出，我们可以用他作为替补。