Question

Describe how you will behave in library in 3 lines?​

Answer 1

1. Obey posted rules. Most libraries have signs on or near the front door stating that particular facility's policy. Read it, commit it to memory, and obey. Doing otherwise can get you a stern look or an escorted trip to the exit. Some of these rules might include expected attire, no food, no drink, and no loud noises.
2. Turn off your phone. Okay, you don't have to turn it off, in case there's an emergency at home. But at least put it on silent/vibrate. And if someone calls you, go outside and answer it. Or if you miss it, go outside and return the call. Talking on your cell phone in a public venue—particularly a place where people are studying or doing research and need to concentrate—is rude and self-centered.
3. Keep the noise down. You don't have to talk in whispers anymore, but you should use your indoor voice. That doesn't mean shouting to someone on the other side of the building. Wait until you are close enough to speak softly and still be heard.