They often leave the tap on when they brush their teeth.

他们经常在刷牙时把水龙头。

We ought to turn out the lights the moment we leave a room, turn off the tap in time, and reuse our textbook and so on.

我们应该要我们离开一间房间的时刻把灯关掉水龙头的时间，并重复使用我们的课本，等等。