Text Three

　　In science, a theory is a reasonable explanation of observed events that are related. A theory often involves an imaginary model that helps scientists picture the way an observed event could be produced. A good example of this is found in the kinetic molecular theory, in which gases are pictured as being made up of many small particles that are in constant motion.

　　A useful theory, in addition to explaining past observations, helps to predict events that have not as yet been observed. After a theory has been publicized, scientists design experiments to test the theory. If observations confirm the scientists' predictions, the theory is supported. If observations do not confirm the predictions, the scientists must search further. There may be a fault in the experiment, or the theory may have to be revised or rejected.

　　Science involves imagination and creative thinking as well as collecting information and performing experiments. Facts by themselves are not science. A the mathematician Jules Henri Poincare said: "Science is built with facts just as a house is built with bricks, but a collection of facts cannot be science any more than a pile of bricks can be called a house."

　　Most scientists start an investigation by finding out what other scientists have learned about a particular problem. After known facts have been gathered, the scientist comes to the part of the investigation that requires considerable imagination. Possible solutions to the problem are formulated. These possible solutions are called hypotheses.

　　In a way, any hypothesis is a leap into the unknown. It extends the scientist's thinking beyond the known facts. The scientist plans experiments, performs calculations, and makes observations to test hypotheses. For without hypotheses, further investigation lacks purpose and direction. When hypotheses are confirmed, they are incorporated into theory.

　　31. Which of the following is the main subject of the passage?

　　A. The importance of models in scientific theories.

　　B. The place of theory and hypothesis in scientific investigation.

　　C. The sorts of facts that scientists find most interesting.

　　D. The ways that scientists perform different types of experiments.

　　32. According to the second paragraph, a useful theory is one that helps scientists to

　　A. find errors in past experiments   B. observe events

　　C. make predictions      D. publicize new findings

　　33. Bricks are mentioned in paragraph 3 to indicate how

　　A. mathematicians approach science

　　B. building a house is like performing experiments

　　C. science is more than a collection of facts

　　D. scientific experiments have led to improved technology

　　34. In the fourth paragraph, the author implies that imaginations are most important to scientists when they

　　A. evaluate previous work on a problem

　　B. formulate possible solutions to a problem

　　C. gather known facts

　　C. close an investigation

　　35. In the last paragraph, what does the author imply is a major function of hypotheses?

　　A. Sifting through known facts

　　B. Communicating a scientist's thoughts to others

　　C. Providing direction for scientific research

　　D. Linking together different theories

　　Text Four

　　If two scientists at Los Alamos National Laboratory are correct, people will still be driving gasoline-powered cars 50 years from now, giving out heat-trapping carbon dioxide into the atmosphere-and yet that carbon dioxide will not contribute to global warming. The scientists, F. Jeffrey Martin and William L. Kubic Jr., are proposing a concept, which they have patriotically named Green Freedom, for removing carbon dioxide from the air and turning it back into gasoline.

　　The idea is simple. Air would be blown over a liquid solution which would absorb the carbon dioxide. The carbon dioxide would then be extracted and subjected to chemical reactions that would turn it into fuel. Although they have not yet built a fuel factory, or even a small prototype, the scientists say it is all bused on existing technology. "Everything in the concept has been built, is operating or has a close cousin that is operating." Dr. Martin said. The proposal does not violate any laws of physics, and other scientists have independently suggested similar ideas.

　　In the efforts to reduce humanity's emissions of carbon dioxide, three solutions have been offered: hydrogen-powered cars, electric cars and biofuels. Biofuels are gasoline substitutes produced from plants like corn or sugar cane. Plants absorb carbon dioxide as they grow, but growing crops for fuel take up wide strips of land. Hydrogen-powered cars emit no carbon dioxide, but producing hydrogen requires energy, and if that energy comes from coal-fired power plants, then the problem has not been solved. The problem with electric cars is that they have typically been limited to a range of tens of miles as opposed to the hundreds of miles that can be driven on a tank of gas.

　　Gasoline, it turns out, is an almost ideal fuel (except that it produces carbon dioxide). If it can be made out of carbon dioxide in the air, the Los Alamos concept may mean there is little reason to switch, after all.

　　"It's definitely worth pursuing." said Martin I. Hoffert, a professor of physics at New York University. "It has a couple of pieces to it that are interesting." Other scientists also said the proposal looked promising but could not evaluate it fully because the details had not been published.

　　36.  What is most remarkable about the proposal made by the two scientists?

　　A.  It is given a patriotic name.

　　B. No law of physics is violated.

　　C.  It is base on existing technology.

　　D.  Carbon dioxide can be converted into fuel.

　　37.  What is the biggest problem with hydrogen-powered cars?

　　A.  There is no cheap source of hydrogen.

　　B.  There might be a safety problem in hydrogen production.

　　C.  They may still be a cause of global warming.

　　D.  They are not suitable for long-distance travel.

　　38. If what is proposed by the two scientists becomes true______

　　A.  air pollution will become a thing of the past

　　B.  there will be no need for gasoline substitutes

　　C.  people will be able to use much cheaper energy

　　D.  there will be no more biofuel-powered vehicles

　　39.  Which of the following can best describe the attitude of Martin I .Hoffert to the proposal?

　　A.  Indifferent   B. Positive  C.  Suspicious   D.  Critical

　　40. The passage is mainly written to________

　　A.  introduce a new concept

　　B.  compare different energy sources

　　C.  stress the importance of gasoline

　　D.  discuss solutions to global warming