Please switch the lights off as you leave.

你离开的时候请把灯关了。

《牛津词典》

Turn the light off as you go out.; Please switch off the lights when you leave.

出门时请随手关灯。

《新英汉大辞典》

Before you start please be sure to switch off all the lights.

出发前请务必把所有的灯关掉。

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