13. We need to be aware of the defects in Internet.
我们要认识到网络的缺点。
还能这样说：
We should notice the disadvantages of computer.
We need be conscious of the shortcomings of Internet.
应用解析：
defect from sth. to sth. 背叛，叛变，投敌，变节
14. They devote most of their time to playing PC games.
他们把大多数时间花在玩电脑游戏上。
还能这样说：
They spend most of time playing computer games.
It takes them plenty of time to play computer games.
应用解析：
devote oneself to sth. 贡献于，献身于;
devoted to sth. 热爱于，踏实于
15. I am fed up with computer games.
我讨厌电脑游戏。
还能这样说：
I take an aversion to online games.
I dislike computer games.
应用解析：
up in 精通;
up-and-coming 进步很大的，很可能成功的;
up sticks 携全部财产迁居别处;
up until sth. 不多于，不迟于，直到