阅读下文，从每小题所给的A、B、C三个选项中选出一个最佳选项。

John is 14 years old. He is a student of Grade Eight. He was a very active and happy boy two years ago. But everything changed after he started to play computer games. He never plays basketball or football with his friends any more. And when he sits in the classroom, he can't listen to the teachers. He sleeps in class. And he spends less and less time in studying. So he gets bad marks in tests. But he is very different after school is over. He stays in the net bar until it is closed. Ah, he loses himself in computer games. His parents can do nothing to stop him. Every morning in the school, when we see that he is so tired after a night's "busy working", we really feel sad. He is too tired!