Not long ago, some of you may have read about the team of mountain climbing scientists who helped to recalculate the elevation of the highest mountain in the world, Mount Everest(珠穆朗玛峰). Of cause the elevation of Mount Everest was determined many years ago using traditional surveying methods. But these scientists wanted to make a more precise measurement, using a new method that takes advantage of recent advances in technology; it’s called the Global Positioning System. The Global Positioning System uses 24 satellites that circle the earth. Each of the satellites is constantly sending out signals, and each signal contains important information that can be used to determine the longitude, latitude and elevation at any point on the earth's surface. Well in order to use the system to calculate Mount Everest’s elevation. Scientists need to put a special receiver on the summit to receive signals from the satellites. The problem with this was that in the past, the receivers were much too heavy for climbers to carry. But now these receivers have been reduced to about the size and weight of a hand-held telephone, so climbers were able to take the receiver to the top of the Everest, and from there, to access the satellite system signals that would allow them to determine the precise elevation. And it turns out that the famous peak is actually a few feet higher than was previously thought.
40, What is the talk mainly about?
41, Why does the speaker mention a hand-held telephone?
42, According to the talk, what probably contributed most to the success of the new study of Mount Everest?
43, In the study described, how were satellite signals used?
Human populations near the equator have evolve dark skin over many generations because the exposure to the fiercest waves of the sun. A similar phenomenon has also occurred in other part of the animal kingdom, the African grass mouse as a good example. Most mice are nocturnal, but the African grass mouse is active during daylight hours. This means that it spends its days searching for food in semi-dry bush and scrub(灌木) habitat of eastern southern Africa. Its fury stripe’s like mice which helps blend in its environment. Because it spends a lot of time in the intense tropical sun, the grass mouse has also evolved two separate safeguards against the sun’s ultraviolet radiation. First, like the populations of humans in this region of world. The skin of grass mouse contains lots of melanin(黑色素) or dark pigment. Second and quite unusual this mouse has the layer of a melanin pigment tissue between the skull and skin. This unique cap provides extra measure protection for grass mouse and three other types African like rodents that active during the day. The only other species scientist have identified the same sort of adaptation is the profit. They do so curled up their head to the sun.
44, What the speaker mainly discussing?
45, What is unusual about the head of African grass mouse?
46, Why do white tent-making bats need protection from sun’s rays?
We are going to start today talking about Congressional aids. That’s the people who worked for our congressional representatives both in Washington and in the representative’s local district. It used to be that members of congress had a relatively a small staff of people working for them. And role of these people wasn’t of primary importance. And now there are thousands of congressional aids. They profoundly affect the way whole government works. Congressional aids work in two different locations, one in the Congressional representative’s local offices, the districts from which they were elected, and two, in Washington. Staff in the local offices help members of Congress stay in touch with citizens of their districts. These citizens can bring problems in person or by mail or phone. This personal connection between the aids and the local people can be helpful when the next election comes around. People remember the help they get from office of their local congressional representatives. But as you know, members of congress have to spend most of their time in Washington taking care of their legislative duties. Over 6000 new laws are introduced in Congress each session, without help, representatives would have trouble keeping up with the proposed laws that directly affect the district. So that’s why the congressional aids play a major role in Washington. They keep the bosses informed about pending legislation, organizing hearings, and just keep their local congress representatives up to date and inform on what’s going on in other parts of Congress. Now another thing congressional aids do is to help develop ideas for laws that their bosses can eventually propose to Congress. This can be called the steps entrepreneurial(企业家的) function. A bit like a business executive trying to find out what product is most popular. Congressional aids promote or encourage laws they think will be popular with the public. You’ve also got other employees that work for whole Congress, not just for individual members, we will talk about these people next.
47. What is the talk mainly about?
48. According to the professor, what do congressional aids at local office mainly do?
49. Why does the professor mention the number of proposed law introduced in Congress?
50. What is the entrepreneurial function of congressional staff members?