I am not clear on which one is the correct answer after reading the following passages. I have attempted an answer. Could you please see if it is correct? (sorry about a long quote here, but I don't have a link for this, otherwise I would have included a link instead)
Radiation occurs from three natural sources: radioactive material in the environment, such as in soil, rock, or building materials; cosmic rays; and substances in 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.Question: It can be inferred from this passage that
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; indeed, the last two decades have witnessed intensified examination and dispute about the effects of low-level radiation, beginning with UN Scientific Committee on the Effects of Atomic Radiation, which reported in 1958: "Even the smallest amounts of radiation are liable to cause deleterious genetic and perhaps also somatic effects."
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 re-examine the assumption that exposure to low linear energy transfer presented only a minor risk.
Recently, examination of the death certificates of former employees of a West Coast plant which produces plutonium for nuclear weapons revealed marked higher rates for cancers of the pancreas, lung, bone marrow and lymph systems than would have been expected in a normal population.
While the National Academy of Sciences committee attributes these differences 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 one percent in the number of serious genetic defects at birth, a possible increase of 1000 disorders per million births.
In the meantime, regulatory efforts have been disorganized, fragmented, and inconsistent, 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.
a. the causes of particular types of cancers can be readily ascertained by identifying the source of radiation.
b. the amount of low-level radiation in the nation has increased measurably since 1958.
c. scientists, by and large, are unconcerned about environmental aspects of cancer causation.
d. the committees on radiation effects of the National Academy of Sciences and of the UN are in disagreement on the impact of low linear energy transfer.
Although the passage says that the West Coast plant employees had lung, lymph , bone marrow and pancreatic cancers, (a) does not seem to be the answer.
It does not say anywhere that since 1958 the low-level radiation has increase nationwide. (b)
Similary, (d) cannot be concluded from the passage.
That leaves (c) as the answer. Is it correct?