第一篇 The Volcano Geologists have been studying volcanoes for a long time. Though they have learned a great deal, they still have not discovered the cause of volcanic action. They know that the inside of the earth is very hot, but they are not sure exactly what causes the great heat. Some geologists have thought that the heat is caused by the great pressure of the earth’s outer layers. Or the heat may be left from the time when the earth was formed. During the last sixty years scientists have learned about radium, uranium, thorium and other radioactive elements. These give out heat all the time as they change into other elements. Many scientists now believe that much of the heat inside the earth is produced by radioactive elements. Whatever the cause of the heat may be, we do know that the earth gets hotter the farther down we dig, in deep mines and oil wells the temperature rises about 10F for each 50 feet. At this rate the temperature 40 miles below the earth’s surface would be over 40000F. this is much hotter than necessary to melt rock. However, the pressure of the rock above keeps most materials from melting at their usual melting points. Geologists believe that the rock deep in the earth may be plastic, or puttylike, in other words, the rock yields slowly to pressure but is not liquid. But if some change in the earth’s crust releases the pressure, the rock melts. Then the hot, liquid rock can move up toward the surface. When the melted rock works its way close to earth’s crust, a volcano may be formed. The melted rock often contains steam and other gases under great pressure. If the rock above gives way, the pressure is released. Then the sudden expansion of the gases causes explosions. These blow the melted rock into pieces of different sizes and shoot them high in the air. Here they cool and harden into volcanic ash and cinders. Some of the material falls around the hole made in the earth’s surface. The melted rock may keep on rising and pour out as lava. In this way, volcanic ash, cinders and lava build up the cone-shaped mountains that we call volcanoes.
A. formation of volcanoes
B. results of volcanic action
C. work of geologists
D. interior of the earth
某本科一专业按如下原则选拔特别奖学金的候选人:将本专业的同学按德育情况排列名次,均分为上、中、下三个等级(即三个等级的人数相等,下同),候选人在德育方面的表现必须为上等;将本专业的同学按学习成绩排列名次,均分为优、良、中、差四个等级,候选人的学习成绩必须为优;将本专业的同学按身体状况排列名次,均分为好与差两个等级,候选人的身体状况必须为好。假设该专业共有36名本科学生,则除了以下哪项外,其余都可能是这次选拔的结果( )
A. 恰好有四个学生被选为候选人
B. 只有两个学生被选为候选人
C. 没有学生被选为候选人
D. 候选人数多于本专业学生的1/4
第二篇 Cell Phones Increase Traffic, Pedestrian Fatalities Cell phones are a danger on the road in more ways than one. Two new studies show that talking on the phone while traveling, whether you’re driving or on foot, is increasing both pedestrian deaths and those of drivers and passengers, and recommend crackdowns on cell1 use by both pedestrians and drivers. The new studies, lead-authored by Rutgers University, Newark, Economics Professor Peter D. Loeb2, relate the impact of cell phones on accident fatalities to the number of cell phones in use, showing that the current increase in deaths resulting from cell phone use follows a period when cell phones actually helped to reduce pedestrian and traffic fatalities. However, this reduction in fatalities disappeared once the numbers of phones in use reached a "critical mass" 3 of 100 million, the study found. These studies looked at cell phone use and motor vehicle accidents from 1975 through 2002, and factored in4 a number of variables, including vehicle speed, alcohol consumption, seat belt use, and miles driven. The studies found the cell phone-fatality correlation to be true even when including factors such as speed, alcohol consumption, and seat belt use. Loeb and his co-author determined that, at the current time, cell phone use has a "significant adverse effect on pedestrian safety" and that “cell phones and their usage above a critical thresholds adds to motor vehicle fatalities." In the late 1980s and part of the 1990s, before the numbers of phones exploded, cell phone use actually had a "life-saving effect" in pedestrian and traffic accidents, Loeb notes. "Cell-phone users’ were able to quickly call for medical assistance when involved in an accident. This quick medical response actually reduced the number of traffic deaths for a time," Loeb hypothesizes. However, this was not the case when cells were first used in the mid-1980s, when they caused a "life-taking effect" among pedestrians, drivers and passengers in vehicles. In those early days, when there were fewer than a million phones, fatalities increased, says Loeb, because drivers and pedestrians probably were still adjusting to the novelty of using them, and there weren’t enough cell phones in use to make a difference in summoning help following an accident, he explains. The "life-saving effect" occurred as the volume of phones grew into the early 1990s, and increasing numbers of cells were used to call 911 following accidents, leading to a drop in fatalities, explains Loeb. But this life-saving effect was canceled out6 once the numbers of phones reached a "critical mass" of about 100 million and the "life-taking effect" - increased accidents and fatalities outweighed the benefits of quick access to 911 services, according to Loeb. Loeb and his co-authors used econometric models to analyze data from a number of government and private studies. He and his co-authors recommend that governments consider more aggressive policies to reduce cell phone use by both drivers and pedestrians, to reduce the number of fatalities.
A. show that talking on the phone while driving or walking in the street increases deaths of drivers and pedestrians.
B. show that talking on the phone while driving increases pedestrian deaths.
C. recommend that strict measures be taken to restrain cell phone use.
D. both A and C.
人脑就是通过这个惊人的微观网络开展它的工作的。每个神经元接收到数千个刺激信号,并立刻决定是中止它还是将信号传给它众多的邻居。在这个过程中,将有数千亿个不同的传输方向。这是人脑与电脑的根本不同。一个电脑基本上是一维的:它操作一个计算,然后是第二个和第三个,是一种线性的形式。它不能同时操作大量不同的工序,并将它们综合平衡而得到一个完整的结果,但人脑能有效地像数千万台电脑同时工作一样地运转。对“人脑能有效地像数千万台电脑同时工作一样地运转”这句话的含义,理解最准确的一项是( )。
A. 人脑可以同时开展大量的线性形式的计算,就好像有千万台电脑同时进行计算一样
B. 人脑通过它的微观网络系统开展工作,就犹如将千万台电脑联网进行某一项工作
C. 人脑可以同时操作不同的工序,就好像数千万台电脑同时进行不同的工作一样
D. 人脑能将不同的信息综合平衡得出一个完整的结果,就好像数千万台电脑同时处理不同信息得出结果一样