信号灯变成了红色，我们必须停下来。

The signal lamp turned red, so we must stop.

在去机场的路上，我们必须停下来加油。

We'll have to stop for fuel on the way to the airport.

如果红灯亮了，你必须停下来。

You must stop if the traffic is red.

科学家必须停下来观察,然后开始思考.

The scientist must stop to observe and start to excogitate.

在生命的漫漫长路上，你都有必须停下来的时候，让他人离开你，无论他们同你多么亲近。

During the course of your life, you will have to stop, and let some people off, no matter how close they are.