有线电视分配系统分配设备空闲端口和分支器输出终端，均应端接（）。 A.50Ω负载电阻

阅读理解。

    Today I will make a speech on zoos. Many people think zoos are cruel and have no place in the modern

world. It is my own opinion that zoos, although not perfect, do have a useful function. Firstly, zoos are

places of education. Zoos can help children to appreciate nature. Furthermore, research into animal behavior

is done in zoos and has increased our knowledge of zoology, genetics and even psychology. Above all, zoos

can protect the future of many species of animal. Many species today are in danger of extinction (灭绝), and

thanks to zoos, they have a chance of survival. Opponents of zoos say that they are cruel. First of all, they

argue zoos cannot recreate the environment in which animals live and because of this, animals are bored and

depressed. Secondly, animals have frequent contact with human visitors, which can be stressful. However,

in my opinion, most zoos have improved recently. It is now quite rare to see animals in cages, and most zoos

try hard to recreate the environments in which different animals live. In conclusion, although zoos are not a

perfect environment for animals, I believe that they have more advantages than disadvantages. In an ideal

world, zoos would not be necessary. But as long as man hunts animals for profit and destroys their

environments, zoos are essential.

1. What is the most important function of zoos according to the writer? [ ]

A. Educating children.

B. Saving rare animals.

C. Recreating an environment.

D. Making a profit.

2. Why are some people against zoos?[ ]

A. Animals make visitors stressful.

B. Animals must live their lives in cages.

C. Animals can feel bored and sad.

D. Animals are in danger of extinction.

3. What does the writer think of zoos?[ ]

A. They are still useful and necessary.

B. They have more disadvantages than advantages.

C. They are a perfect environment for animals.

D. They are recreative places for animals.

4. Many animal species can remain because ______. [ ]

A. they live in the zoos

B. children help them

C. they can see other animals in the zoos

D. the animals are cruel

5. Most zoos are ______. [ ]

A. getting worse and worse

B. getting smaller and smaller

C. getting better and better

D. more and more popular

6. It's ______ to keep the animals live in the cages according to the passage. [ ]

A. safe

B. creative

C. necessary

D. cruel

Stephen Hawking believes that the earth is unlikely to be the only planet _______ life has developed gradually.

A．that

B．where

C．which

D．whose

既能使溴水褪色，又能使酸性KMnO₄溶液褪色的是

A．苯

B．乙烯

C．乙醇

D．氯化铁

高处作业人员使用安全带时，必须系挂在作业上部的牢靠处，高挂低用。（）

15米金属拉梯由上、中、下三个梯节、支撑杆以及升降装置组合而成。