My 12-year-old daughter asks me: "Why can't I have my own cellphone? Everyone else in my class have one. Without a cellphone, I cannot make friends with them, and I cannot join their conversations. I feel lonely and sad." How to properly respond to my daughter? Shall I give her a cellphone or not?

Dear daughter, I truly understand your feeling, and I don't want to keep you feel bad at school. I'm willing to give you anything that I can reasonably afford that makes you happy. However, I have some concerns that giving you a cellphone might harm you instead of making you happier. Can you address my concerns and make me feel safe to give you the cellphone? Here are some of my concerns:
1. Using cellphone too much would harm your eye sight. Especially for teenagers, whose eyes are still growing, it's very easy to have near-sight pretty quickly.
2. Using cellphone too much would take too much of your time, and you would spend less time reading books, doing exercises, playing outside, talking to people, which harms your overall development. Adults like me already ready lots of books, did lots of exercises, and talked to a lot of people when I was a teenager, so I already developed those skills.
3. Using cellphone too much would make you feel hard to focus on one thing. The scattered information would stimulate your attention, and make you feel excited at superficial contents, and don't think deeply.
4. You might accidentally lost your cellphone, and you will feel sad about it. Teenagers usually are more likely to lost things than adults in general.