下图反映近20年来我国人口 [ ] A．总量不断减少 B．总量增加一倍 C．增长

一个导体两端加4 V电压时，通过它的电流为0.8 A，该导体的电阻是     Ω；当把它两端电压变为8 V时，通过它的电流为__   _A。若电压为零V，它的电阻为   Ω。

鸡内金的药用部位为()

A．干燥砂囊内壁

B．干燥内壳

C．干燥卵鞘

D．干燥体

E．干燥分泌物

A、B、C、D、E、F为原子序数依次增大的六种元素。已知：A是周期表中原

子半径最小的元素．B的基态原子核外电子有 7种运动状态，B、C、E三种元素原子中未

成对电子数之比为3：2：1，D原子核外有4个能级且均充满电子，D与E可形成DE₂型化

合物，F原子核外最外层只有1个电子，其余各层均充满电子。

回答下列问题：

（1）写出下列元素的名称：B         C         E          

（2）F在周期表位位于       区，与F同周期且未成对电子数最多的元素为       ­（填

写元素符号），该元素价电子排布图为          ；

（3）B与D组成的化合物可以与水反应，写出它与水反应的化学方程式               

在面侧深区从翼外肌上缘穿出的神经为( )

A．嚼肌神经
B．耳颞神经
C．颊神经
D．下齿槽神经
E．翼内肌神经

The population conference in Brasilia has now ended. One of the aims of the conference was for countries from each continent to look back at past experiences and to learn from them for the future.

In Europe

Population problems are different in different parts of the world.  For example, in many European countries the population is getting older. The birth rate is very low because many young people have only one child or none at all. People are living longer, too. On average, men tire to 76 and women to 78. By 2050 around 25 % of the population of some European countries will be over 60 years old.

This change has happened very fast within two generations. If governments had expected this change, they would have encouraged people to prepare more for old age. At the moment many old people are very lonely and often very poor. If people had expected to live so long, they would probably have saved more money for their retirement.

In Africa

In Africa, the problems of the future will be very different. There, the population is doubling every 24 years. Many families continue to have large numbers of children to look after older people and to help on the land. However, better medical services have increased life expectancy and more children survive to become adults. Research shows that the size of the family is connected with the standard of women’s education. If more girls had gone to school in the last 20 years, family size in Africa would probably not have continued to be so big.

In Asia

In contrast, the problem in Asia is not just population growth but also overcrowding in many cities. Traditionally, most people have lived in the countryside, but within the next 25 years more than 65% will live in cities. If Asian countries had expected this kind of change 20 years ago, they would have tried to provide more work and better education in the countryside. This is starting to happen now, but it may be too late.

56. What is the cause of African population problem?

A. Low birth rate and increased life expectancy. B. More older people, more children.

C. People’s moving from the countryside to the cities.

D. Better medical services and increased life expectancy.

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

A. In Europe it is normal to live to be 76 or more.

B. Medicine has changed population patterns.

C. Population problems are the same everywhere.

D. Many old people in Europe experience poverty.

58. What can be inferred from the passage?

A. Cities everywhere are becoming larger and larger.

B. Asian countries have tried to provide more work for people.

C. A lot of girls couldn’t go to school in Africa.

D. The older people in Europe are, the lonelier they will be.