问题
选择题
使用显微镜时，下列哪种组合看到的视野最暗（ ）
A．P和甲
B．R和丙
C．R和甲
D．P和丙
答案
甲乙丙一端无螺纹为目镜，PQR有螺纹为物镜．显微镜的放大倍数=物镜倍数×目镜倍数．物镜倍数越高，镜头越长；目镜倍数越高，镜头越短；
其目镜和物镜的组合是短目镜丙和长物镜R，放大倍数最大；这种组合的视野最暗．
故选B
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使用显微镜时，下列哪种组合看到的视野最暗（ ）
A．P和甲
B．R和丙
C．R和甲
D．P和丙
甲乙丙一端无螺纹为目镜，PQR有螺纹为物镜．显微镜的放大倍数=物镜倍数×目镜倍数．物镜倍数越高，镜头越长；目镜倍数越高，镜头越短；
其目镜和物镜的组合是短目镜丙和长物镜R，放大倍数最大；这种组合的视野最暗．
故选B
| 完形填空 | |||
| Every school has its own rules. How many 1 are there in your school? At some schools, the students 2 to wear uniforms on school days. But many students don’t like to wear uniforms. They think the uniforms are the ugliest 3 in the world. But the school don’t allow students to wear 4 own clothes at school. So some students draw cartoons or some famous singers on their 5 . They think it is very 6 that everyone wears the same. It is very unfair(不公平的) that teachers and students are wearing 7 . But most of the students 8 the rules. What do you think 9 it? Do you 10 your school uniforms? | |||
| ( )1. A. students ( )2. A. has ( )3. A. clothes ( )4. A. their ( )5. A. school bags ( )6. A. bored ( )7. A. same ( )8. A. obey ( )9. A. of ( )10. A. like | B. rules B. must B. shirts B. they B. books B. boring B. differently B. agree B. about B. make | C. uniforms C. should C. skirts C. them C. uniforms C. interesting C. different C. listen C. by C. wash | D. rulers D. have D. cloth D. themselves D. desks D. interested D. the same D. listen to D. for D. put on |