For decades many U. S. veterans who took part in atmospheric nuclear tests have wondered whether their exposure to radiation might ultimately cost them their lives. Their private fears became a public issue in 1976 after a veteran claimed his leukemia was caused by radiation from a 1957 test series.The atomic veterans and their families, as well as researchers and policy-makers, continue to struggle for definitive answers. These have been elusive, at least in part, because a crucial piece of information has been difficult to get-the radiation dose that each individual received.In the largest study to date, researchers from the Institute of Medicine (IOM) have come up with some partial answers. But they too were limited in their ability to draw conclusions by the lack of usable information on radiation exposure.The new study focused on participants in five series of nuclear tests, all of which took place either in the Nevada desert or the South Pacific. Nearly 70, 000 soldiers, sailors, airmen, and marines were involved in at least one of these, and about 30 percent of them have now died. For comparison, researchers selected a group of 65, 000 military people serving at the same time under similar conditions, except that they did not take part in nuclear tests.After an intensive review of service and death records, researchers found no difference between the two groups in overall death rates or in total deaths from cancer. Had there been a dramatic radiation effect, it would have shown up in this comparison.The researchers also analyzed specific causes of death, including diseases linked in other studies to radiation. Here there were some differences. Among the nuclear test veterans, 14 percent more died from leukemia than those in the comparison group, although the difference lacked statistical significance and could have resulted from chance.When comparisons were made based on whether the veterans participated in nuclear tests in Nevada or in the Pacific Ocean, the differences were sharper: a 50 percent higher leukemia death rate among Nevada atomic veterans than among the comparison group. This was not true among Pacific test participants, who actually had a slightly lower, though not statistically significant leukemia death rate than those in their comparison group.81.The passage tells us that researchers wish that they could find out______.A.when and where the veterans received the nuclear radiationB.why the amount of radiation cannot be accurately measuredC.who was responsible for the veterans' deathsD.how much radiation each veteran got during the nuclear tests82.The latest study includes a comparison made between______.A.healthy veterans and unhealthy veteransB.nuclear test participants and those with no radiation exposureC.the veterans who are still alive and those who have diedD.people who died of cancer and people who took part in atomic tests83.What can we learn about the result of the latest study?A.There was a significant difference in total deaths from cancer between the two groups.B.There was no significant difference in death rates between the two groups.C.The comparison group has a lower death rate.D.More veterans died from leukemia than from other cancers.84.One comparison mentioned in the last paragraph was made between______.A.Pacific test participants and those who undertook the Nevada testB.Nevada atomic veterans and those who didn't take part in any nuclear testsC.Veterans in Nevada and Pacific atomic tests and the comparison groupD.half of Nevada test participants and half of the group of no test participants85.How different is the group of Nevada test participants from their South Pacific counterparts?A.The former shows a higher leukemia death rate than the comparison group.B.The former shows a lower leukemia death rate than the comparison group.C.The former shows a higher death rate than the latter.D.The former shows a lower death rate than the latter.