阅读下面材料，在空白处填入适当的内容(1个单词)或括号内单词的正确形式，并将答案填写在答题卡相应的位置上。
It is reported that many middle school students are just not getting enough sleep, especially during the school week. The problem seems to get       (bad) as they get older. Year 7 students sleep 8.4 hours in a school night, and Year 9 students only 6.9 hours.
It’s also reported that not getting enough sleep can cause       ( (problem) in a student’s life. Many students fall       (sleep) in school or while doing their homework, so it is not       (surprise) that they get lower grades than those who get enough sleep. Scientists suggest nine hours a night for middle school students.
Of the students who feel      (happy) and nervous, 73% don’t get enough sleep at night.
Why aren’t students getting enough sleep? Many students have one of the     (follow) things, like telephone, television, or computer in their bedrooms. Using them on a school night not       (takes their time away from homework, but also makes       difficult for them to sleep. As a result, many students can’t sleep before 11 p.m, yet they must get up early      (go) to school.
Scientists also suggest students should not do exciting activities for an hour        bedtime.