单选题阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。 {{B}}Avalanche and Its Safety{{/B}} An avalanche is a sudden and rapid flow of snow, often mixed with air and water, down a mountainside. Avalanches are{{U}} (51) {{/U}}the biggest dangers in the mountains for both life and property. All avalanches are caused by an over-burden of material, typically snowpack, that is too massive and unstable for the slope{{U}} (52) {{/U}}supports it. Determining the critical load, the amount of over-burden which is{{U}} (53) {{/U}}to cause an avalanche,{{U}} (54) {{/U}}a complex task involving the evaluation of a number of factors. Terrain slopes flatter than 25 degrees or steeper than 60 degrees typically have a low{{U}} (55) {{/U}}of avalanche. Snow does not{{U}} (56) {{/U}}significantly on steep slopes; also, snow does not{{U}} (57) {{/U}}easily on flat slopes. Human-triggered avalanches have the greatest incidence when the snow's angle of rest is{{U}} (58) {{/U}}35 and 45 degrees; the critical angle, the angle at which the human incidence of avalanches is greatest, is 38 degrees. The rule of thumb is: A slope that is{{U}} (59) {{/U}}enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle. Additionally, avalanche risk increases with{{U}} (60) {{/U}}; that is, the more a slope is disturbed by skiers, the more likely it is that an avalanche will occur. Duc to the complexity of the subject, winter travelling in the backcountry is never 100% safe. Good avalanche safety is a continuous{{U}} (61) {{/U}}, including route selection and examination of the snowpack, weather{{U}} (62) {{/U}}, and human factors. Several well-known good habits can also{{U}} (63) {{/U}}the risk. If local authorities issue avalanche risk reports, they should be considered and all warnings should be paid{{U}} (64) {{/U}}to. Never follow in the tracks of others without your own evaluations; snow conditions are almost certain to have changed since they were made. Observe the terrain and note obvious avalanche paths where plants are{{U}} (65) {{/U}}or damaged. Avoid traveling below others who might trigger an avalanche.

单选题She seemed to have detected some anger in his voice.

单选题There is always excitement at the olympic Games when an athlete Ubreaks/U a record.

单选题She eventually married the most persistent one of her admirers.

单选题Environmental Protection The destruction of our natural resources and contamination of our food supply continue to occur, largely because of the extreme difficulty in affixing (把…固定) legal responsibility on those who continue to treat our environment with reckless abandon (放任). Attempts to prevent pollution by legislation, economic incentives and friendly persuasion have been met by lawsuits, personal and industrial denial and long delays-not only in accepting responsibility, but more importantly, in doing something about it. It seems that only when government decides it can afford tax incentives or production sacrifices, there is any initiative for change. Where is industry's and our recognition that protecting mankind's great treasure is the single most important responsibility? If ever there will be time for environmental health professionals to come to the frostiness and provide leadership to solve environmental problems, that time is now. We are being asked, and, in fact, the public is demanding that we take positive action. It is our responsibility as professionals in environmental health to make the difference. Yes, the ecologists, the environmental activists and the conservationists serve to communicate, stimulate thinking and promote behavioral change. However, it is those of us who are paid to make the decisions to develop, improve and enforce environmental standards, I submit, who must lead the charge. We must recognize that environmental health issues do not stop at city limits, county lines, state or even federal boundaries. We can no longer afford to be tunnel-visioned in our approach. We must visualize issues from every perspective to make the objective decisions. We must express our views clearly to prevent media distortion and public confusion. I believe we have a three-part mission for the present. First, we must continue to press for improvements in the quality of life that people can make for themselves. Second, we must investigate and understand the link between environment and health. Third, we must be able to communicate technical information in a form that citizens can understand. If we can accomplish these three goals in this decade, maybe we can finally stop environmental degradation, and not merely hold it back. We will then be able to spend pollution dollars truly on prevention rather than on bandages.

单选题Parents have become increasingly Uconcerned about/U the television viewing habits of their children.

单选题Senator James Meeks has called off a boycott of Chicago Public Schools, organized to protest Illinois' education funding system.A. reclaimedB. proposedC. indulgedD. canceled

单选题These are defensive behavior patterns which derive from our fears.

单选题Please put up your bands if you have any questions.A. raiseB. reachC. waveD. fold

单选题The laws which the new government Uimposed/U on the population were very harsh.

单选题The council meeting terminated at 2 o"clock.

单选题阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。 {{B}}Captain Cook Arrow Legend{{/B}} It was a great legend while it lasted, but DNA testing has{{U}} (51) {{/U}}ended a two-century-old story of the Hawaiian arrow carved from the bone of British explorer Captain James Cook{{U}} (52) {{/U}}died in the Sandwich Islands in 1779. "There is{{U}} (53) {{/U}}Cook in the Australian Museum," museum collection manager Jude Philip said not long ago in announcing the DNA evidence that the arrow was not made of Cook's bone. But that will not stop the museum from continuing to display the arrow in its{{U}} (54) {{/U}}"Uncovered: Treasures of the Australian Museum," which{{U}} (55) {{/U}}include a feather cape presented to Cook by Hawaiian King Kalani 'opu'u in 1778. Cook was one of Britain's great explorers and is credited with{{U}} (56) {{/U}}the "Great South Land,"{{U}} (57) {{/U}}Australia, in 1770. He was clubbed to death in the Sandwich Islands, now Hawaii. The legend of Cook's arrow began in 1824{{U}} (58) {{/U}}Hawah'an King Kamehameha on his. deathbed gave the arrow m William Adams, a London surgeon and relative of Cook's wife, saying it was made of Cook's bone after the fatal{{U}} (59) {{/U}}with islanders. In the 1890s the arrow was given to the Australian Museum and the legend continued{{U}} (60) {{/U}}it came face-to-face with science. DNA testing by laboratories in Australia and New Zealand revealed the arrow was not made of Cook's bone but was more{{U}} (61) {{/U}}made of animal bone, said Philp. However, Cook's fans{{U}} (62) {{/U}}to give up hope that one Cook legend will prove true and that part of his remains will still be uncovered, as they say there is evidence not all of Cook's body was{{U}} (63) {{/U}}at sea in 1779. "On this occasion technology has won," said Cliff Thornton, president of the Captain Cook Society, in a{{U}} (64) {{/U}}from Britain. "But I am{{U}} (65) {{/U}}that one of these days ...one of the Cook legends will prove to be true and it will happen one day."

单选题When the United States stock market fell in 1929, many stockholders were forced to sell their shares at {{U}}ludicrously{{/U}} low prices.

单选题It is said the houses along this street will soon be demolished.A. pulled downB. pulled upC. pulled offD. pulled in

单选题The cards that are wildly used now are credit.cards.

单选题The depiction of the lives of black people in the south is graphic .

单选题下面的短文后列出了7个句子，请根据短文的内容对每个句子做出判断：如果该句提供的是正确信息，请选择A；如果该句提供的是错误信息，请选择B；如果该句的信息文中没有提及，请选择C。 {{B}}Radiocarbon Dating{{/B}} Nowadays scientists can answer many questions about the past through a technique called radiocarbon (放射性碳),or carbon-14,dating. One key to understanding how and why something happened is to discover when it happened. Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at the University of Chicago. An atom of ordinary carbon, called carbon-12, has six protons (质子)and six neutrons (中子)in its nucleus(原子核). Carbon-14,or C-14,is a radioactive,unstable form of carbon that has two extra neutrons. It returns to a more stable form of carbon through a process called decay(衰减). This process involves the loss of the extra neutrons and energy from the nucleus. In Libby's radiocarbon dating technique, the weak radioactive emissions (放射)from this decay orocess are counted by instruments such as a radiation detector and counter. The decay rate is used to determine the proportion of C-14 atoms in the sample being dated. Carbon-14 is produced in the Earth's atmosphere when nitrogen(氮)-14,or N-14, interacts with cosmic rays(宇宙射线). Scientists believe since the Earth was formed, the amount of nitrogen in the atmosphere has remained constant. Consequently,C-14 formation is thought to occur at a constant rate. Now the ratio of C-14 to other carbon atoms in the atmosphere is known. Most scientists agree that this ratio is useful for dating items back to at least 50,000 years. All life on Earth is made of organic molecules(分子)that contain carbon atoms coming from the atmosphere. So all living things have about the same ratio of C-14 atoms to other carbon atoms in their tissues(组织). Once an organism(有机体)dies it stops taking in carbon in any form, and the C-14 already present begins to decay. Over time the amount of C-14 in the material decreases, and the ratio of C-14 to other carbon atoms goes down. In terms of radiocarbon dating,the fewer C-14 atoms in a sample,the older that sample is.

单选题We packed up the things we had accumulated (积累) over the Ulast/U three years and left.

单选题Red giant stars do not become white dwarf stars abruptly ; the process takes more than fifteen hundred years.

单选题I had the very pleasure of ______ with your husband in the meeting last week.A. knowledgeB. identificationC. acquaintanceD. recognition