例句
The police had backup from the army.
警方得到了军方的增援。
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。
a backup power supply
备用电源
The police had backup from the army.
警方得到了军方的增援。
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。
a backup power supply
备用电源