3 sentences

1. 离开房间时请随手关灯。

   lí​kāi fáng​jiān shí qǐng suí​shǒu guān​dēng.

   Please turn off the lights as you leave the room.

   Source: Dong Chinese Dictionary

2. ‎谁上了厕所没关灯？

   ‎ shéi shàng le cè​suǒ méi guān​dēng?

   Who used the bathroom and didn't turn off the light?

   Source: OpenSubtitles

3. 为什么要关灯？

   wèi​shén​me yào guān​dēng?

   Why turn off the lights?

   Source: OpenSubtitles