GMAT阅读新题练习:Passage 95

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　　Passage 95

　　Radiation occurs from three natural sources: radioactive material in the environment, such as in soil, rock, or building materials; cosmic rays; and substances in the human body, such as radioactive potassium in bone and radioactive carbon in tissues. These natural sources account for an exposure of about 100 millirems a year for the average American.

　　The largest single source of man-made radiation is medical X rays, yet most scientists agree that hazards from this source are not as great as those from weapons test fallout, since strontium 90 and carbon 14 become incorporated into the body, hence delivering radiation for an entire lifetime. The issue is, however, by no means uncontroversial. The last two decades have witnessed intensified examination and dispute about the effects of low-level radiation, beginning with the United Nations Scientific Committee on the Effects of Atomic Radiation, which reported in 1958 that “even the smallest amounts of radiation are likely to cause deleterious genetic and perhaps also somatic effects (somatic effects: [核]躯体效应).”

　　A survey conducted in Britain confirmed that an abnormally high percentage of patients suffering from arthritis of the spine who had been treated with X rays contracted cancer. Another study revealed a high incidence of childhood cancer in cases where the mother had been given prenatal pelvic X rays. These studies have pointed to the need to reexamine the assumption that exposure to low-linear energy transfer (linear energy transfer: [核]线能量传递, 线性能量转移) presents only a minor risk.

　　Recently, examination of the death certificates of former employees of a West Coast plant that produces plutonium for nuclear weapons revealed markedly higher rates for cancers of the pancreas, lung, bone marrow (bone marrow: n. 骨髓), and lymphatic system (lymphatic system: n.淋巴系统) than would have been expected in a normal population.

　　While the National Academy of Sciences committee attributes this difference to chemical or other environmental causes rather than radiation, other scientists maintain that any radiation exposure, no matter how small, leads to an increase in cancer risk. It is believed by some that a dose of one rem, if sustained over many generations, would lead to an increase of 1 percent in the number of serious genetic defects (genetic defects: 遗传缺陷) at birth, a possible increase of 1,000 disorders per million births.

　　In the meantime, regulatory efforts have been disorganized, fragmented, inconsistent, and characterized by internecine strife and bureaucratic delays. A Senate report concluded that coordination of regulation among involved departments and agencies was not possible because of jurisdictional disputes and confusion. One federal agency has been unsuccessful in its efforts to obtain sufficient funding and manpower for the enforcement of existing radiation laws, and the chairperson of a panel especially created to develop a coordinated federal program has resigned.

　　1. The primary purpose of the passage is to

　　(A) explain the difference between natural and man-made radiation

　　(B) arouse concern about the risks connected with exposure to radiation

　　(C) criticize the United Nations Scientific Committee on the Effects of Atomic Radiation

　　(D) advocate limiting the use of atomic weapons testing, since the fallout is extremely hazardous(B)

　　(E) publicize the results of British medical survey

　　2. Which of the following, according to the passage, is a list of three natural sources of radiation?

　　(A) Radioactive potassium in bone, strontium 90, uranium ore

　　(B) Carbon 14 in tissues, cosmic rays, X rays

　　(C) Cosmic rays, radioactive potassium in bones, radioactive carbon in tissues

　　(D) Plutonium, radioactive material in rock, strontium 90(C)

　　(E) X rays, carbon 14, plutonium

　　3. Which of the following does the author cite in support of the quotation from the United Nations Scientific Committee on the Effects of Atomic Radiation (lines 18-20)?

　　I. Strontium 90 and carbon 14 become incorporated into the body and deliver radiation for an entire lifetime.

　　II. An abnormally high percentage of patients with arthritis of the spine who were treated with X rays subsequently contracted cancer.

　　III. A high incidence of cancer appeared among children of mothers who had been given prenatal pelvic X rays.

　　(A) I only

　　(B) II only

　　(C) I and II only

　　(D) II and III only(D)

　　(E) I, II, and III

　　4. The passage contains information that answers which of the following questions?

　　(A) How many millirems of radiation from man-made sources is the average American exposed to each year?

　　(B) Is exposure to radiation linked to any other diseases besides cancer?

　　(C) How many types of radiation are there?

　　(D) What is the maximum level of radiation to which humans can safely be exposed?(E)

　　(E) Why is exposure to the fallout from weapons testing considered by some to be more hazardous than exposure to X rays?

　　5. According to the passage, some scientists believe that a dose of one rem of radiation continued over a period of generations would

　　(A) raise the strontium 90 levels in the body but otherwise have little effect

　　(B) relieve the acute suffering of those afflicted with arthritis of the spine without side effects

　　(C) have the effect of increasing by 1 percent the cases of serious genetic defects

　　(D) have little impact on the regulatory efforts of federal agencies(C)

　　(E) cause an additional 1,000 per million cases of cancer of the bone marrow or lymphatic system

　　6. It can be inferred from the last paragraph of the passage that the chairperson who resigned from the panel to develop a coordinated federal program for radiation regulation most likely did so because

　　(A) he or she disagreed with the findings of the Senate committee

　　(B) his or her agency could not obtain funding or manpower for implementation of existing laws

　　(C) he or she supported the position of the National Academy of Sciences committee and opposed regulation of radiation exposure

　　(D) he or she was disorganized and inconsistent in chairing the panel(E)

　　(E) regulatory efforts have been balked by disputes, confusion, and bureaucratic delays

　　7. The passage contains evidence suggesting that it was most likely written

　　(A) in 1958

　　(B) by a British scientist

　　(C) for the journal of the National Academy of Sciences

　　(D) by a lobbyist for the defense industry(E)

　　(E) in the late 1970s

　　8. The passage implies that each of the following statements about radiation has been disputed EXCEPT?

　　(A) Even small doses of radiation are likely to cause birth defects.

　　(B) Exposure to low-linear energy transfer presents only a minor risk.

　　(C) Many small doses of radiation are as harmful as a single large dose.

　　(D) Humans can tolerate a certain amount of radiation.(D)

　　(E) Exposure to radiation causes cancer.

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