原发性腹膜炎的主要致病菌为（） A．大肠杆菌 B．厌氧类杆菌 C．溶血性链球菌 D．

阅读理解。

     It is reported that many middle school students are just not getting enough sleep, especially during the

school week. The problem seems to get worse 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 problems in a student's life. Many students fall

asleep in school or while doing their homework, so it is not surprising 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 unhappy and nervous, 73％ don't get enough sleep at night. Why aren't students

getting enough sleep?Many students have one of the following things, like telephone, television, or computer,

in their bedrooms.Using them on a school night not only takes their time away from homework,but also makes

it difficult for them to fall asleep.As a result, many students can't fall asleep before 11 P.m.., yet they must

get up early to go to school.

     Scientists also suggest students should not do exciting activities for an hour before bed time.

1. According to the report, who might get the most sleep?

A. Year 7 students.

B. Year 8 students.

C. Year 9 students.

D. Year 10 students.

2. How many hours of sleep do middle school students need each night?

A. Seven hours.

B. Nine hours.

C. Ten hours.

D. Twelve hours.

3. Not getting enough sleep can cause the following problems EXCEPT ______.

A. falling asleep in class

B. getting lower grades

C. falling asleep while doing homework

D. getting fatter and fatter 60.What might be the best tit

4. What might be the best title for the passage?

A. Early to Bed, Early to Rise

B. Students' Life at Sehool

C. Students Don't Sleep Enough

D. How to Get Enough Sleep

理想光学系统有何特点？

我国地势自西向东可分为三级阶梯，下列作为第一、二级阶梯分界线的是( )。

A．昆仑山—阿尔金山—祁连山—横断山—线
B．大兴安岭—太行山—巫山—雪峰山—线
C．大兴安岭—阴山—贺兰山—巴颜喀拉山—冈底斯山—线
D．阴山—贺兰山—巴颜喀拉山—冈底斯山—线

财政收入中最主要的部分是( )。

A．税收

B．国债

C．国有企业上缴利润

D．规费

发达国家在实施反倾销时，针对发展中国家的产品，如果倾销幅度低于（）或损害是微不足道的，以及原产于一个发展中国家成员的倾销产品数量不足进口国同类产品总量的3%，则终止倾销调查

A、2%

B、3%

C、4%

D、5%