平行光管在经纬仪与平行光管组成的光学测量系统中的作用是测定一个测量的参考系。

论述权利与义务的关系。

党的十五大指出，20世纪以来我们的民族经历了哪三次历史性巨大变化？

如图所示为一理想变压器，原线圈匝数为n₁，四个副线圈的匝数均为n₂，四个副线圈中负载电阻的阻值R_a=R_b=R_c=R_d，D为理想二极管。现从原线圈P，Q两端输入正弦交变电流，那么下列说法正确的是

A．只有流过R_a和R_d上的电流仍是交变电流

B．加在R_a两端的电压是R_b的两倍

C．R_a消耗的功率是R_b的两倍

D．若输入的正弦交变电流频率增大，R_c的功率增大，R_d的功率减小

A person may have an idea about himself that will prevent him from doing good work.

He may have the belief that he is not capable (有能力的) of it. A child may think he is __1__ because he doesn’t understand how to make the __2__ of his mental faculties (才能). Older people may be mistaken that they are incapable of learning things new because of their __ 3__.

A person who believe that he is incapable will not make a real __4__ because he feels that it would be useless. He won’t go at a job with confidence necessary for __5__ , and he won’t  work his hardest way, even though he may think he is doing so. He is __6__ likely to fail, and the failure will __7__ his belief in his competence (才能) .

Alfred Alder, a famous doctor, had __8__ like this. When he was a small boy, he had a poor __9__ in maths. His teacher told his parents he had no ability in maths in order that they would not __10__ too much of him. In this way, they two __11__ the idea. He accepted __12__ mistaken thinking of his ability, felt that it was useless to __13__ and was very poor at maths, __14__ as they expected.

One day he worked at a problem which __15__ of the other students had been able to solve.

Alder __16__ in solving the problem. This gave him confidence (信心). He now __17__ with interest, determination and purpose, and he soon became especially good at __18__. He not only proved that he could learn maths well, but luckily he learned __19__ in his life from his own experience that if a person goes at a job with determination and purpose, he may __20__ himself as well as others by his ability.

1. A. clever                   B. shy                   C. useless                     D. stupid

2. A. biggest                 B. most                 C. highest                     D. deepest

3. A. ability                  B. age                   C. brain                        D. knowledge

4. A. decision                B. success              C. effort                       D. trouble

5. A. work                    B. study                C. improvement            D. success

6. A. truly                       B. really                C. however                   D. therefore

7. A. lead to                 B. strengthen         C. increase                    D. add to

8. A. an experience        B. an example        C. a thought                  D. a story

9. A. state                        B. mind                 C. start                         D. ending

10. A. blame                 B. expect               C. get                           D. win

11. A. developed           B. organized          C. discovered                D. found

12. A. his                     B. her                   C. its                          D. their

13. A. manage               B. succeed             C. try                         D. act

14. A. only                   B. almost               C. just                        D. then

15. A. none                   B. no                    C. no one                   D. nobody

16. A. gave                   B. succeeded          C. failed                            D. believed

17. A. lived                  B. worked             C. played                    D. graduated

18. A. lessons                  B. medicine           C. subjects                  D. maths

19. A. early                  B. deeply               C. late                        D. simply

20. A. encourage           B. love                  C. astonish                  D. disappoint

决定刺激性气体致病部位和程度的因素是

A．浓度
B．脂溶性
C．浓度和溶解度
D．溶解度
E．浓度和脂溶性