1 . All that noise makes it hard to c______(集中注意力). (根据中英文提示单词拼写)

2 . The medicine always made him feel sleepy and unable to c________(集中注意力).(根据中英文提示填空)

3 . Her friend Laura Williams told me she had trouble c________ (集中，全神贯注于) on what the teachers said in class. (根据中英文提示填空)

4 . I couldn't c______ (集中精力于) on the experiment. （根据中英文提示填空）

5 . With his attention c_______（集中）on his book，he didn’t notice his mother entering his room. （根据汉语提示单词拼写）