主要是指一个国家或地区的经济发展状况的是（） A.市场需求 B.市场竞争 C.顾客心

阅读理解。

     Where do you think people will live in the future? Can you predict people will work and live in the sea? But

how will people go to work then? By submarine (潜水艇) Some scientists believe that some day submarine will

be as many as today's cars. A famous French drivers says 'One day,man will work on the ocean floor as they

do on the street!'

      If people want to live in the sea, they have to solve a lot of problems, similar to those of living on the moon, are lack of oxygen (氧气) and weightlessness (失重). Many questions are hard to solve. For example, what

will happen to our bodies if we live in the sea for a very long time? Scientists are looking for answers.

     Maybe in 50 years man will be able to live in the sea,away from the crowded and noisy cities on land. Man

will find it fun and interesting to live in the sea. And life in the sea is more comfortable. Don't you think so?

1. Maybe people in the future wil l______ to work on the ocean floor.

A. drive a car

B. take a bus

C. take a submarine

D. swim

2. People have to ______ first before living in the sea.

A. build houses

B. learn to swim

C. learn to drive submarine

D. solve some problems

3. What problem will people have if they live in the sea?

A. They will have difficulty in breathing.(呼吸)

B.They will become quite short.

C. They will feel cold.

D. They will feel tired.

4. The writer thinks living in the sea is ______ than living on land

A. more comfortable

B. less comfortable

C. easier

D. more crowded

5. Which of the following is NOT true according to the passage?

A. There are also some problems for people to solve if they want to live in the sea.

B. The sea is noisy and crowed for man to live in.

C. Some of the problems are very hard to solve.

D. Some scientists believe submarines will be popular in the future.

TD抗原

A．只能引起体液免疫

B．只能引起细胞免疫

C．只能诱导产生IgG类抗体

D．只能诱导产生IgM类抗体

E．可诱导产生免疫记忆

若某商品需求的收入弹性为负，则该商品为低档品。（）

下列哪个选项是合法的标识符

A．123

B．_name

C．class

D．1first

一次侧未并列运行的两组电压互感器，禁止（）。