英语(专科起点本科)3A 一、阅读理解 （共20题,共40分） 1. Despite the fact that today viruses (病毒) are known to cause cancer in animals and in certain plants, there exists a great reluctance to accept viruses as being of importance in human cancer. Basic biological phenomena generally do not differ strikingly as one goes from one species to another. It should be recognized that cancer is a biological problem and not a problem that is unique to man. Cancer originates when a normal cell suddenly becomes a cancer cell which multiplies widely and without apparent restraint. Cancer may originate in many different kinds of cell, but the cancer cell usually continues to carry certain traits (特性) of the cell of origin. The transformation of a normal cell into a cancer cell may have more than one kind of cause, but there is good reason to consider the relationships that exist between viruses and cancer. Since there is no evidence that human cancer, as generally experienced, is infectious, many persons believe that because viruses are infectious agents they cannot possibly be of importance in human cancer. However, viruses can mutate (突变) and examples are known in which a virus that never kills its host can mutate to form a new strain of virus that always kills its host. It does not seem unreasonable to assume that a harmless latent virus might mutate to form a strain that causes cancer. Certainly the experimental evidence now available is consistent with the idea that viruses as we know them today could be the causative (引起的) agents of most, if not all cancer, including cancer in man. （10分） (1) According to the passage, cancer cells are _. （2分） A.similar to the cell of origin B.mutations of viruses C.unable to reproduce D.among the smallest cell known .标准答案：A (2) The best title for this passage is _. （2分） A.New Light on the Causes of Cancer B.The Newest Theory on the Nature of Viruses C.Viruses and cancer D.On the Nature of Life .标准答案：C (3) Cancer should be considered to be a biological problem rather than a medical one because _. （2分） A.viruses are known to cause cancer in animals B.at present, human cancer is not believed to be infectious C.there are many known causes for the transformation of a normal cell to a cancer cell D.results of experiments on plants and animals do not vary greatly from species to species .标准答案：D (4) Many people believe that viruses cannot possibly be of importance in human cancer because _. （2分） A.they are harmless agencies B.they are the causative agents of most human cancer C.they seem to be infectious to many people D.they are generally thought to be relevant to most cancer in man .标准答案：C (5) The possibility that a virus causes human cancer is indicated by _. （2分） A.the fact that viruses have been known to mutate B.the fact that a cancer-immune (免疫的) individual may lose his immunity C.the fact that production of human cancer cells might be due to a genetic factor D.the fact that man is host to many viruses .标准答案：A 2. We all know that it is possible for ordinary people to make their homes on the equator, although often they may feel uncomfortably hot there. Millions do it, but as for the North Pole - we know that it is not only a dangerously cold place, but that people like you and me would find it quite impossible to live there. At the present time only the scientists and explorers can do so, and they use special equipment. Men have been traveling across and around the equator on wheels, on their feet or in ships for thousands of years; but only a few men, with great difficulty and in very recent time, have ever crossed the ice to the North Pole. So it may surprise you to learn that, when traveling by air, it is really safer to fly over the North Pole than over the equator. Of course, this is not true about landings in the polar region (which passenger aeroplanes do not make), but the weather, if we are flying at a height of 5,000 meters above the Pole, is a delight. At 4,000 meters and more above the earth you can always be sure that you will not see a cloud in the sky as far as the eye can reach. In the tropics, on the other hand, you are not certain to keep clear of bad weather, even at such heights as 18,000 or 20,000 meters. Aeroplanes cant climb as high or as quickly in cold air as in warm. Nor can clouds. In practice, this is an advantage to the aeroplane, which is already at a good height when it reaches the polar region and so does not need to climb, while at the same time cold air keeps the clouds down low. （10分） (1) The polar region is _. （2分） A.a good place to land at by aeroplane B.a good place to fly over C.a good place to live in D.a good place to cross .标准答案：B (2) It is a delight to fly at the Pole because there _. （2分） A.planes fly higher than at the equator B.the eyes can reach about 4,000 meters C.planes fly more quickly than at the equator D.planes are clear of bad weather .标准答案：D (3) Aeroplanes usually do not need to climb quickly or fly high in the pola