Questions 46 to 50 are based on the following passage.
Most forest fires are caused by human carelessness or ignorance. Forest fire prevention, therefore, is mainly a problem of creating better understanding of the importance of forests, an awareness of the danger of fire in the woods, and a sense of personal responsibility to safeguard the forests from danger. This is not an easy job.
Careless smokers are responsible for thousands of forest fires each year. Many of these are started when cigarette butts (烟蒂) and matches are thrown from automobiles. Others are caused by hunters, hikers (徒步旅行者), fishermen, or woods workers who are careless in disposing of their smoking materials. The Forest Service has posted rules in many of the National Forests that prohibit smoking except in certain designated areas. Many of the states have laws against throwing lighted materials from automobiles. The prevention of smoker-caused fires, however, depends upon changing the attitudes and behavior of millions of people who smoke in hazardous areas.
The most important natural cause of fire is lightning (闪电). This accounts for 11 percent of forest fires on protected land for the entire nation. In the Western States, lightning causes a much higher percentage of fires than it does in the East.
Advances in knowledge of fire weather are helping forest protection forces to know when to be alert to lightning-caused fires. Adequate and well-equipped forces can control them quickly and hold the damage to a minimum. Experiments in “seeding” thunder clouds to prevent or control the lightning itself have been in process for many years, but new breakthroughs are needed for any significant reduction in the fires lightning starts.
46. This passage is chiefly about __________.
A. smoking in forests
B. changing the attitudes and behavior of millions of people
C. the chief causes of forest fires and their prevention
D. advances in knowledge of fire weather
47. Preventing smoker-caused forest fires is mainly a problem of __________.
A. building the proper knowledge and habits in human beings
B. safeguarding the forests from fire
C. posting rules in forests
D. holding the damage to a minimum
48. Lightning-caused fires can be controlled quickly by __________.
A. holding the fire damage to a minimum
B. people who have changed their attitudes and behavior
C. enough fire fighters with good fire-fighting devices
D. carrying out experiments in “seeding” thunder clouds
49. “Alert to” (Line 2, Para. 4) most probably means __________.
A. aware of B. watchful for
C. responsible for D. busy with
50. Which of the following statements is true according to the passage? __________.
A. It is difficult to prevent forest fires
B. Smoking is allowed only in certain forests
C. 11% of the forest fires in the Western States are caused by lightning
D. Experiments in “seeding” thunder clouds have helped reduce lightning-caused forest fires
Questions 51 to 55 are based on the following passage.
Some years ago industries had more freedom than they have now, and they did not need to be as careful as they must today. They did not need to worry a lot about the safety of the new products that they developed. They did not have to pay much attention to the health and safety of the people who worked for them. Often new products were dangerous for the people who used them；often conditions in the work place had very bad effects on the health of the workers.
Of course sometimes there were real disasters(灾难) which attracted the attention of governments and which showed the need for changes．Also scientists who were doing research into the health of workers sometimes produced information which governments could not ignore．At such times, there were inquiries into the causes of the disasters or the problems. New safety rules were often introduced as a result of these inquiries；however, the new rules came too late to protect the people who died or who became seriously ill.
Today many governments have special departments which protect customers and workers. In the U. S., for example, there is a department which tests new airplanes and gives warnings about possible problems. It also makes the rules that aircraft producers must follow. Another department controls the foods and drugs that companies sell．A third department looks at the places where people work，and then reports any companies that are breaking the laws which protect the health and safety of workers. Of course，new government departments and new laws cannot prevent every accident or illness，but they are having some good results. Our work places are safer and cleaner than before. The planes and cars which we use for travel are better. Producers are thinking more about the safety and health of the people who buy and use their products．
51.The main topic of the passage is _________.
A. conditions in the work place B. the freedom of industries in the past
C. changes in industrial production D. the safety and health of workers and customers
52. It can be inferred from the passage that in the past _________.
A. workers often got ill because of the poor working conditions
B. companies were free to put out any products they wanted to
C. many people were killed by dangerous products
D. industries were as careful in management as they are today
53. It is implied in the passage that _________.
A. governments and companies had different opinions about the safety of products
B. governments paid little attention to the safety of products
C. government officials often did not listen to scientists
D. in the past no safety laws were introduced by governments
54. Some years ago safety rules _________.
A. were put forward due to scientists’ recommendations
B. came into being as a result of the workers’ demands
C. were introduced because quite a number of people were killed or seriously injured
D. were effective enough to protect workers and customers
55. The special departments protect customers and workers in many ways EXCEPT
A. testing new products B. controlling the sale of products
C. designing new products D. inspecting work places