The most pressing nuclear energy issue is the disposal of nuclear waste. Even if all the reactors in existence were completely s

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问题     The most pressing nuclear energy issue is the disposal of nuclear waste. Even if all the reactors in existence were completely safe to operate, there would still be unsolved issue of what to do with the waste from generating electricity by means of nuclear energy. Those who claim that they feel comfortable with nuclear energy are, none the less, concerned about waste disposal methods. Seven states, including California, have put the building of nuclear plants on hold until legislators are convinced that there is a safe way to dispose of the radioactive waste from the plants.
    In the meantime, pools of liquid waste and piles of solid waste from private industry and governmental bomb production grow. Since 1962, the volume of radioactive waste produced by the nuclear power industry has amounted to about 4,300 cubic meters. By the end of the twentieth century, if production continues at the same rate, there will be 40,000 cubic meters of nuclear waste.
    Power plants and bomb-making are not the only sources of waste. Uranium mining and milling operations have dumped 24 million metric tons of radioactive tailing wastes at dumping sites around the nation. At places where uranium is currently milled, there is another 100 million metric tons of tailings. Uranium tailings are solid materials in the slurry(or watery mixture)of depleted ore-bearing rock, chemicals, and liquids that result from milling. Usually, the slurry is piped to holding ponds. When a uranium mill goes out of business, the ponds are left to evaporate, uncovering piles of dried tailings. Uncovered piles of tailings give off radioactive radon gas. Once in the air, the gas finds its way into the water supply and the food chain. Consequently, many nuclear experts agree that uranium mill tailings may be more dangerous than high-level radioactive wastes from reactors and bombs.
It can be inferred from the passage that the most dangerous by-product of uranium mining and milling is______.

选项 A、solid mining wastes
B、the slurry in which the waste is stored
C、the radon gas that is emitted by the waste
D、the uranium that is recovered in the mining operations

答案C

解析 推断题。选项中的内容在文中均有提及,但是从危害性上讲,选项A、B、D都没有直接说到它们的害处,而文中第三段讲到Uncovered piles of tailings give off radioactive radon gas.Once in the air,the gas finds its way into the water supply and thefood chain.故可推断出这种放射性气体才是最有害的。故选项C正确。
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