German scientist think that your brain keeps working while you're asleep.To show that they were right，they gave two groups of students a problem to work out Group One went to sleep，and Group Two stayed awake. （1）　 　

    At the same time，from a recent study many children have missed out on 4.500 hours of sleep by the time they are seven years old.According to the Ministry of Education，primary school students should get at least 10 hours of sleep a night. （2）　　 The answer is nine.If they don't get enough sleep at night，they will face more challenging situations in schoolwork.

Schools are taking action to make sure the students can get enough sleep.

（3）　　 Three reasons are mentioned for the problem.Firstly they spend hours n scrolling（滚动），such as Douyin and Wechat Hours of watching the mobile phones can be harmful to their eyes and cause students to sleep less. （4）　　They may work overtime to get the job finished and they can't watch over he kids.Lastly，drinks like tea or coffee can also keep them excited and awake.

    （5）　　For example，they should avoid using mobile phones too much，and drink something like milk before going to bed.

    Only if schools，families and students join hands together，can students get enough sleep and be at their best in schoolwork.

阅读短文，把 A﹣E五个句子填入文中空缺处，使短文内容完整。

A.But researchers say many students still sleep less. B.In fact，students themselves should also take sleep seriously. C.Secondly，busy parents may not remind them to go to bed at the proper time. D.Then how many hours of sleep should junior high school students get a night？ E.The result showed the students who slept worked out the answer more quickly.