问题 单项选择题

规模经济是指产出的增加速度快于投入的增加速度。这里的“规模”即是指由生产能力的扩大而导致的较大生产批量。这里的“经济”,是指成本的节约、效益的提高或报酬的递增。 根据以上定义,下列不属于规模经济的是( )。

A.一家工厂生产一辆自行车要投入10小时劳动,在成本不变的情况下,投入5000小时,产500辆车。工厂规模扩大后,生产5000辆车,只要30000小时的劳动时间。

B.一家工厂原年产钢500万吨,投入1亿资本,5000人,在技术水平不变的条件下,投入增加一倍,年产钢1000万吨。

C.甲企业的生产影响到乙企业,因其影响是正的,则甲企业的生产低于社会最优水平,但把他们合二为一,则此时的外部影响就“消失”了。

D.瑞士集中了大量生产手表的企业,形成较大的产业规模,既提高了效率,又降低了成本。

答案

参考答案:B

解析: B项的投入与产出的单位效益没有变化,不是规模经济。

选择题
阅读理解

阅读理解

     Now, we know that if we do not get enough vitamins, we are at risk of developing a number of

diseases. As a result, vitamin supplements(补品),though expensive, are popular with people who

worry that they are not getting enough vitamins from the foods they eat. But contrary to what many

people think, medical experts have found little evidence that most supplements do anything to improve

health or protect against disease.

     In fact, medical experts warn that taking too many of some vitamins can be harmful. For example,

too much vitamin E can cause bleeding. People should discuss what vitamins they take with their doctors,

as some vitamins can produce harmful side effects when mixed with medicines.

     Experts, however, do say that sometimes vitamins can help prevent disease. People who know they

lack a particular vitamin should take vitamin supplements. Some older adults, for example, may not have

enough vitamin B-twelve. This is because, as people get older, their body loses its ability to take it from

foods. Also, people who spend much time inside may need some extra vitamin D as the skin makes this

vitamin from sunlight.

     Different vitamins are found in different foods. Vitamin A is found in fish liver oil. It also is in the

yellow part of eggs. Sweet potatoes, carrots and other darkly colored fruits and vegetables contain

substances that the body can change into vitamin A. Vitamin B-twelve is found in green leafy vegetables

and other foods, like fruits. Vitamin K can be found in pork products.

     In fact, for most people, a balanced diet can ensure enough of the vitamins our bodies need. So, it is

important for us to eat a mixture of foods every day to ensure that we get enough vitamins our bodies

need.

1. What is probably talked about before this passage?

A. How many vitamins a person's body needs.  

B. How many vitamins some foods contain.

C. The benefits that vitamins bring to our health.

D. What people should do to stay healthy.

2. Vitamin supplements are popular with people because ________.  

A. people mistakenly think that they are good for their health

B. they contain more vitamins than the foods people eat

C. food does not provide enough vitamins people need

D. people fear that a lack of vitamins will lead to disease

3. From the passage, we can learn that medical experts advise people _________.

A. never to take any vitamin supplements  

B. to depend only on food for their vitamins

C. not to take any vitamins together with medicines

D. to consult doctors before taking vitamin supplements

4. For people who lack Vitamin B-twelve, they can eat more from _______.

A. sweet potatoes  

B. green leafy vegetables  

C. pork products  

D. eggs