SHOULD

Reason 1: Teenagers have little time left for homework.

Examples/Facts/Explanations: Teenagers spend too much time watching online videos, checking social media, or playing computer games.

Reason 2: Too much screen time is bad for teenagers' health.

Examples/Facts/Explanations: Too much screen time can damage eyesight, reduce sleep time, and cause weight gain

SHOULDN'T

Reason 1: Quality of screen time is more important than quantity.

Examples/Facts/Explanations: Teenagers can learn a lot of useful knowledge and necessary skills through online educational games and videos. 

Reason 2: The gap between teenagers and parents may become wider.

Examples/Facts/Explanations: Teenagers may think their parents are not fair to them.