They make threats but back down at the first sniff of trouble.

　　他們起先氣勢洶洶，但一看情形不妙立刻軟了下來。

　　I'll take you back down to the valley.

　　我會(huì)帶你返回下面的山谷里。

　　His determination and refusal to back down had won the day

　　他的堅(jiān)定和拒不退讓使他贏得了勝利。

　　It's too late to back down now

　　現(xiàn)在打退堂鼓已經(jīng)太晚了。

　　I drove back down the highway at normal speed

　　我以正常車速沿公路返回。