H-21：have somebody at one's back 让别人支持某人
A:Tom should learn to look after himself.
A:汤姆应该学会照料自己了。
B:Yeah. he can't always have us at his back.
B：没错，他不能总指望我们支持他。
A:Let's talk to him about it.
A:咱们跟他谈谈吧。
B:OK. It is the time.
B:好的，是时候了。
