1 . But spending too much time online is unhealthy and makes it very difficult to f________(集中，特别关注)other things in life. (根据中英文提示填空)

2 . While reading, you should ________ ________(集中精力于) the sentences’ idea, not the single word. （根据汉语提示完成句子）

3 . With all his attention ____(集中) his work, he didn’t notice what happened outside.