Actually, the world’s birth rate is falling. But so is death rate, as medical advances have made it possible for man to live longer than before. Such advances have also reduced baby death rate. Unless population growth is reduced, the world population may reach 12 billion in a century. Is the earth capable of providing a good life for so large a population? 

11. A population explosion will lead to _________. 
A. a lot of social problems         B. medical advances 
C. a decrease in food production     D. a worse life in every country 

12. It took _______year for world population to grow form 1 billion to 3 billion. 

A. 100   B. 115   C. 130   D. 145 

13. By the year 2000, today’s ____ nations will have a total population of 5 billion people, nearly four fifths of the world’s population. 
A. biggest   B. Asian   C. developing   D. developed 

14. ________, the world may have a population of 12 billion in a century. 
A. If man can live longer in the future 
B. If the science of medicine is developing fast enough 
C. If the population growth is not reduced 
D. If the earth is able to provide a good life for more people 

15. This passage tells us that _________ 
A. the United Nations thinks it possible to avoid a population explosion 
B. 5. 1 billion people are living in the undeveloped countries 
C. in advanced nations the population growth is being controlled 
D. the world’s population is increasing 

Passage 4 

Questions 16 to 20 are based on the following passage. 

A scientist who wants to predict the way in which consumers(消费者) will spend their money must study consumer behavior. He must obtain data both on the resources of consumers and on the motives that tend to encourage or discourage money spending. 

If an economist were asked which of three groups borrow most — — —people with rising incomes, Stable incomes, or decreasing incomes — — — he would probably answer, those with decreasing incomes. Actually years 1947— 1950,the answer was: people with rising incomes. People with decreasing incomes were next and people with stable incomes borrowed the least. This shows us that traditional assumptions(假设) about earning and spending are not always reliable. Another traditional assumption is that if people who have money expect prices to go up they will hasten to buy. If they expect prices to go down, they will postpone buying. But research surveys have shown that this is not always true. The expectations of price increases may not stimulate buying. One typical attitude was expresser by the wife of a mechanic in an interview at a time of rising prices. “In a few months,” she said, “we’ll have pay more for meat and milk; we’ll have less to spend on other things. “Her family had been planning to buy a new car but they postponed this purchase. Furthermore, the rise in prices that has already taken place may be disliked and buyer’s resistance may be produced. This is shown by the following typical comment: “I just don’t pay these prices; they are too high.”