问题 单项选择题

pH3.4和pH5.4的溶液,其H浓度相差多少倍

A.1

B.2

C.5

D.20

E.100

答案

参考答案:E

解析:
pH是H浓度的负对数,所以这两种pH的溶液H浓度相差100倍。

完形填空
完形填空。
     Steve Morris was not a typical child. But when he was nine, his    1    to be typical was very strong.
Of all the people Steve remembered, one woman, his primary-school teacher, Mrs Beneduci,    2     in
his mind. Mrs Beneduci was a wise person. She realized that mere words to a kid    3     not carry much
weight. So instead, with the secret aid of a little mouse, she found a    4    to show Steve his real talent.
     One day Mrs Beneduci began her   5    with the question: who was Abraham Lincoln? Amy was
required to answer it. She said in a   6    voice, "Uh…he, uh, had a beard." The students burst into 7     . "Steve?" said the teacher. Steve stood up and   8   confidently, "He was the 16th President of the United
States."
       9    with Steve's performance, the teacher then added that Abraham Lincoln had been President
during the Civil War…Then she stopped,      10    she was listening to something. It sounded like a
mouse. The little girls screamed. Some stood on their chairs. Mrs Beneduci tried to    11    the students
down, and asked Steve to find the poor little creature.
     Steve sat straight up in his chair and asked everybody to be     12    . In the sudden stillness he
raised  his head, hesitated for a moment, and   13     to the wastebasket. "He's right over there!" said
Steve   14     " I can hear him!"
     And so he was: a frightened little mouse that was    15    beneath  the wastepaper, hoping to go
   16    . Nature gave him a remarkable pair of    17    to make up for his blindness. In the heart of
small, sightless Steve a pride was born, and that pride is with him still.     18     the incident,
Mrs Beneduci would continue to     19     his talent, and she always reminded Steve of the little
mouse.
     A little mouse gave a small boy     20    . Steve Morris is now a singer who is popular all over the
world.
( )1.  A. limit        
( )2.  A. stands out  
( )3.  A. will        
( )4.  A. control      
( )5.  A. rest        
( )6.  A. low          
( )7.  A. tears        
( )8.  A. decided      
( )9.  A. Satisfied    
( )10. A. even when    
( )11. A. calm        
( )12. A. relaxed      
( )13. A. pointed      
( )14. A. slowly      
( )15. A. running      
( )16. A. undiscovered
( )17. A. arms        
( )18. A. Before      
( )19. A. test        
( )20. A. excitement  
B. desire      
B. turns up    
B. shall        
B. chance      
B. holiday      
B. proud        
B. laughter    
B. predicted    
B. Confused    
B. so that      
B. lie          
B. anxious      
B. walked      
B. proudly      
B. escaping    
B. unexplained  
B. hands        
B. In          
B. encourage    
B. patience    
C. direction    
C. gets through  
C. might        
C. power        
C. study        
C. long          
C. cheers        
C. answered      
C. Thrilled      
C. just because  
C. keep          
C. quiet        
C. fell          
C. carefully    
C. fighting      
C. untreated    
C. legs          
C. After        
C. inspect      
C. warmth      
D. courage          
D. gives away      
D. must            
D. choice          
D. class            
D. clear            
D. applause        
D. required        
D. Surprised        
D. as though        
D. settle          
D. active          
D. rushed          
D. luckily          
D. struggling      
D. unhurt          
D. ears            
D. For              
D. feel            
D. confidence      
单项选择题

A very important world problem, if not the most serious of all the great world problems which affect us at the moment, is the increasing number of people who actually inhabit this planet. The limited amount of land and land resources will soon be unable to support the huge population if it continues to grow at its present rate.

In an early survey conducted in 1888, a billion and a half people inhabited the earth. Now, the population exceeds five billion and is growing fast—by the staggering figure of 90 million in 1988 alone. This means that the world must accommodate a new population roughly equal to that of the United States and Canada every three years! Even though the rate of growth has begun to slow down, most experts believe the population size will still pass eight billion during the next 50 years.

So why is this huge increase in population taking place It is really due to the spread of the knowledge and practice of what is becoming known as "Death Control". You have no doubt heard of the term "Birth Control"—" Death Control" is something rather different. It recognizes the work of the doctors and scientists who now keep alive people who, not very long ago, would have died of a variety of then incurable diseases. Through a wide variety of technological innovations that include farming methods and sanitation, as well as the control of these deadly diseases, we have found ways to reduce the rate at which we die—creating a population explosion. We used to think that reaching seventy years old was a remarkable achievement, but now eighty or even ninety is becoming recognized as the normal life-span for humans. In a sense, this represents a tremendous achievement for our species. Biologically this is the very definition of success and we have undoubtedly become the dominant animal on the planet. However, this success is the very cause of the greatest threat to mankind.

Man is constantly destroying the very resources which keep him alive. He is destroying the balance of nature which regulates climate and the atmosphere, produces and maintains healthy soils, provides food from the seas, etc. In short, by only considering our needs of today we are ensuring there will be no tomorrow.

An understanding of man’s effect on the balance of nature is crucial to be able to find the appropriate remedial action. It is a very common belief that the problems of the population explosion are caused mainly by poor people living in poor countries who do not know enough to limit their reproduction. This is not true. The actual number of people in an area is not as important as the effect they have on nature. Developing countries do have an effect on their environment, but it is the populations of richer countries that have a far greater impact on the earth as a whole.

The birth of a baby in, for example, Japan, imposes more than a hundred times the amount of stress on the world’s resources as a baby in India. Most people in India do not grow up to own cars or air-conditioners—nor do they eat the huge amount of meat and fish that the Japanese child does. Their life-styles do not require vast quantities of minerals and energy. Also, they are aware of the requirements of the land around them and try to put something back into nature to replace what they take out.

For example, tropical forests are known to be essential to the balance of nature yet we are destroying them at an incredible rate. They are being cleared not to benefit the natives of that country, but to satisfy the needs of richer countries. Central American forests are being destroyed for pastureland to make pet food in the United States cheaper; in Papua New Guinea, forests are destroyed to supply cheaper cardboard packaging for Japanese electronic products; in Burma and Thailand, forests have been destroyed to produce more attractive furniture in Singapore and Japan. Therefore, a rich person living thousands of miles away may cause more tropical forest destruction than a poor person living in the forest itself.

In short then, it is everybody’s duty to safeguard the future of mankind-not only through population control, but by being more aware of the effect his actions have on nature. Nature is both fragile and powerful. It is very easily destroyed; on the other hand, it can so easily destroy its most aggressive enemy—man.

Which of the following recommendations might be made by the author()

A. Increasing food and industrial production, and encouraging people in undeveloped countries to have fewer children

B. Improving education about the environment and banning the export of wood products from poor to rich countries

C. Encouraging people worldwide to have fewer children and to behave in a more responsible way towards nature

D. Restricting population worldwide and increasing the use of nonrenewable resources