题目内容
According to the passage, all of the following are sources of radioactive waste EXCEPT ______.
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Section B
Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C and D. You should decide on the best choice.
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 ______.
听力原文： Windbreaks are barriers formed by trees and other plants. Farmers plant these barriers around their fields to protect their land.
Windbreaks stop the wind from blowing soil away (33) . They also keep the wind from destroying or damaging crops. They are very important for protecting grain crops.
There have been studies done on windbreaks in parts of West Africa, for example. These found that grain harvests can be twenty percent higher in fields protected by windbreaks compared to fields without such protection (33) .
But windbreaks seem to work best when they allow some winds to pass through them (341. If the wall of trees and plants blocks the wind completely, then violent air motions will take place close to the ground. These motions will lift soil into the air where it will be blown away.
There should be at least two lines in each windbreak. one line should be large treas. The second line, right next to it, can be shorter trees and other plants with leaves. Locally grown trees and plants are best for windbreaks.
If the quality of the land is not very good, studies have shown that one kind of tree that can grow well is the white pine (35) .
Windbreaks not only protect land and crops from the wind. Surplus trees can be cut down and used to provide wood (33) .
(34)
A．When there are two lines of plants in each windbreak.B．When there is space left for
Darwin's great work, The Origin of Species, is now generally accepted as one of the most important books ever written. But when it first came out in 1859, it was both derided and bitterly condemned by scientists and laymen.
Much of opposition to The Origin of Species arose from Darwin's claim that all living creatures, including man, are somehow related. Many people were outraged by the suggestion that man shared a common ancestor with animals such as apes and monkeys. They attacked Darwin for saying that man had descended from the apes.
But Darwin never actually said this. He believed that modern men and modern apes have both descended from the same ancestor. But at some time in pre-history, millions of years ago, men and apes began to develop separately, and ever since have continued to take on different characteristics. Today, more than 90 years after Darwin's death, this is the opinion which scientists continue to hold.
In his works, Darwin described the progression of life from its earliest forms. First came the invertebrate-creatures without a backbone. Then invertebrates evolved into fish; fish into amphibians; amphibians into reptiles; and reptiles into birds and mammals.
Fossil remains found after his death show that Darwin was right. Perhaps the most amazing fact about his theory is that he managed to work it out with the aid of only a few fossil discoveries.
Fossil remains were not the only information which we now possess but which Darwin lacked. He did not know that apes have the same diseases as men; nor that they and men have the same kind of blood. Nor did he know about the modern uses of radiation which enable scientists to tell the age of fossil remains and so estimate the speed at which evolution has taken place.
Which of the following best describes the passage as a whole？
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