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。
You can't have one without the other, as the song says
就像歌里唱的那样，两者密不可分，不能只取其一。
My three guitars broke one after the other
我的3把吉他陆续都坏了。
Sybil ate three biscuits, one after the other
西比尔接连吃了3块饼干。
He looked from one to the other of them, then salaamed and left.
他扫了他们每个人一眼，行了个额手礼就离开了。