The reasons why a teenager shouldn't have a CP.

Hi [이름]!
Thank you for the good composition. I had fun reading it. Anyway, just be careful with your grammar particularly on the plural form of words and word choices as well. Anyway, keep sending  your compositions to refine your skills further. Enjoy the day and take care! See you later!

Actually as telecommunications technologies develop, we can not force teenager not to use the cell phone.
>>Actually as telecommunication technologies develop, we cannot force teenagers not to use cell phones.
Because they need to use the cell phone to communicate with friends, parents, etc..
>>Because they need to use a cell phone to communicate with friends and parents etc..
But they have to know relation with time they use the cell phone and 
school performance.
>> But they have to know how to balance the use of cellphone and their school performance.
Those who use the cell phone all day are hindered in their study.
>>Correct
So teenager have to control using time for cell phone.
>> So teenager must control the time they use their cellphones.
If teenager can control using time, I think they have to use the cell phone. ^^
>>If they can control the time they are using cellphone, they can have cellphone.^^