Scientists know that our weight，mental health and immune （免疫） system are connected to our sleep habits.So are your grades — to a surprising degree，a new study finds.It showed that sleep caused nearly one-fourth of the difference among students' grades in a class.So even if you spend hours studying for a test but get too little and inconsistent （不一致的） sleep，you might still do poorly.And boys with poor sleep habits seemed to suffer （遭受） most.
   Jeffrey Grossman，a scientist at the Massachusetts Institute of Technology in Cambridge wanted to test sleep in the real conditions.People's sleep timetables are often disordered and unpredictable.He wanted to find out if the sleep connects performance in exams.To find out，his team turned to Fitbits.These wrist （手腕） bands can follow how long people sleep and how often they wake up.
   The researchers invited 100 around 18-year-old students.Each got a Fitbit to wear all term long.At the end of the term，the scientists looked at the students' sleep data （數(shù)據(jù)）.They especially paid attention to patterns （模式） in the days and weeks before exams.They then compared those patterns to the students' test scores.The results showed the importance of sleep for students.
   As expected，teens who stirred （微動(dòng)） a lot during the night were likely to perform poorly.The same went for those who didn't get enough sleep.But how much someone slept the night before an exam didn't affect that person's grade.So，is pulling an all-nighter before the big test okay？No，it turns out.That's because there was a third important factor （因素）：consistency of sleep a week and even a month before an exam.That means "a student who sleeps seven hours at night，every night，will do better than a student who sleeps 7.5 hours one night and 6.5 another night，" Grossman says.That was true even when both students got the same amount （數(shù)量） and quality （質(zhì)量） of sleep.
   Sleep length，quality and consistency together caused 24.4% of the difference among the students' test grades.And these factors appeared especially important for boys.Grossman's team is not sure why.But boys who didn't get enough sleep or regular sleep were likely to do worse in an exam than girls who had similar sleep patterns.
   Helping students get more sleep partly depends on schools starting their days later.But more importantly，students themselves must have a clear idea of the importance of good sleep.That may require getting more sleep and cutting down late evening use of phones and other screens.Even if you have plenty of after-school activities，schoolwork and a social life，you still need to get your sleep.

（1）The researchers used Fitbits to

D

D

.
A．help the students sleep well
B．predict the students' sleep length
C．improve the students' grades
D．collect the students' sleep data
（2）What can we learn from the research？

C

C

A．Students with the same quality of sleep have no difference in grades.
B．Students who sleep for more hours are likely to have higher grades.
C．Boys with poor sleep habits appear to suffer more than girls.
D．Staying up before a big test can make a good result in grades.
（3）Which of the following best shows the structure of the passage？

A

A

（①=Para.1，②=Para.2，③=Para.3，...）
A．
B．
C．
D．
（4）The best title for this passage is

A

A

A．Sleep：Is quality important？
B．Sleep：Does it influence grades？
C．Sleep：Is 7.5 hours enough？
D．Sleep：Does it depend on schoolwork？