在关系数据模型中，一个关系中的主码( )。A．可以取值为NULL(空值) B．只能

藏獒，跛行，呈三脚跳。左后肢膝外翻，膝关节屈曲，趾尖向外，小腿向外旋转。最可能患（）

A.髋关节前方脱位

B.髋关节后方脱位

C.髌骨上方脱位

D.髌骨内方脱位

E.髌骨外方脱位

小明在一张日历上圈出一个竖列且相邻的三个日期，算出它们的和是48，则这三天分别是[ ]

A．6，16，26

B．15，16，17

C．9，16，23

D．不确定

阅读理解

     Doctors' moonlighting is becoming popular in hospitals around China. It has not only raised a lot of

heated discussions in the media, but also caught the attention of the central government in Beijing.

     On December 26, a spokesman of the Ministry of Health stressed that the ministry was firmly against

doctors' moonlighting, while strict regulations should be applied to doctors taking part-time jobs, the

Xinhua News Agency reported.

      Last year, the Ministry sent out a notice to a variety of health organizations to speed up the reform

of their personnel (人事) system. According to the notice, medical organizations can hire medical experts

as part-time doctors but such activities should take place under the hospital's management and regulations(规定).

     As for moonlighting--meaning that the doctor provides medical service without the permission of the

original hospital--such activity goes against China's Practicing Doctor Law, Xinhua reported.

     In China, doctors used to be controlled by hospitals and they could work for only one hospital.

However, as China's medical personnel system reform developed, it has been recognized that medical

human resources, just like human resources in other areas, should be shared by the whole society. But

on the other hand, doctors' taking part-time jobs should follow the relative regulations applied in the

medical field.

     First of all, they should follow relative government laws and regulations. They should also follow the

rules and regulations set by the medical organizations they work for. In addition, they should pay taxes

for their income from the part-time jobs. What matters most is that they should first finish their regular

jobs as required and be responsible for patients to ensure qualified and safe medical treatment.

1. What is the greatest difference between moonlighting and taking part-time jobs?

A. Doctors can earn more money by moonlighting than by taking part-time jobs.

B. Doctors pay fewer taxes for the money made by moonlighting than by taking part-time jobs.

C. Taking part-time jobs is permitted by hospitals while moonlighting is-against the present regulations.

D. Doctor's part-time jobs, instead of moonlighting, are encouraged by health organizations.

2. From this passage we know that doctors are allowed to        nowadays.

A. only work for one hospital        

B. work for more than one hospital

C. work any time when they are free  

D. be out of control of hospitals

3. The passage is taken most probably from           .

A. a notice sent out by the Ministry of Health  

B. regulations made by health organizations

C. China's Practicing Doctor Law

D. a magazine or a newspaper

4. According to the passage, we have got to know that         .

A. all doctors around China prefer moonlighting to part-time jobs

B. moonlighting has been permitted by China's practicing Doctor Law

C. taxes should be paid for the money doctors get from their part-time jobs

D. strict management policies have been adopted to direct the moonlighting

图中所示硬脊膜穿破后的头痛的发生原理，请问其发生率约为（）

A.10%

B.11%～19%

C.20%～29%

D.30%～76%

E.80%

送电前应确认电动扳手上开关断开状态，以防送电后电动扳手突然转动，存在造成人员伤害的危险。