Why does the professor point out that 20,000 jobs for musicians disappeared at the end of the silent-film era?
A. To explain that many movie theaters closed at the end of the silent-film era
B. To explain that live music had lost popularity
C. To illustrate the huge demand for musicians during the silent-film era
D. To emphasize the number of jobs created by the production of sound movies
在题干中非常明确的问到为什么提及20,000 jobs for musicians disappeared也就是说提到20000个工作机会没有了的目的是什么呢？
在原文中教授强调了无声电影时期电影院是音乐人较好的工作选择高薪且工作需求量大We are talking a period of maybe thirty years where working in movie theaters was the best job for musicians. It was very well-paid.The rapid growth of the film industry meant movie theaters were popping up everywhere.
由此产生了很多工作岗位，多到什么程度呢？后面 So suddenly there was this huge demand for musicians. In fact, over 20,000 jobs for musicians were gone, disappeared at the end of the silent-film era, 20,000. Ok. So from the beginning, music was a big part of film, even at the first… 在这个部分教授强调这个数字20,000，强调了两遍，目的非常明显了，主要起到强调失业人数多的作用。既然在无声电影末期有如此多的人失业这也说明在无声电影真的给音乐人给了很多工作岗位，所以第二题的答案应该是C选项To illustrate the huge demand for musicians during the silent-film era。
According to the professor,what is the significance of having a satellite in orbit about 36,000 kilometers above Earth's surface?
A. This is the physical limit of the length that a carbon nanotube cable could reach.
B.A satellite orbiting at this height can remain directly above on location on Earth.
C. Earth's gravitational field is too weak to hold a satellite in orbit at higher altitudes.
D. The distance around Earth's equator is approximately 36,000 kilometers.
题干中文到卫星在地球上方约36,000千米的高度环绕的意义是什么？在这篇文章中教授提出了一个要利用电梯运载物体到太空的想法，而电梯不会凭空转动，需要用一个绳子挂起来，原文中提到elevators don’t just rise up. They have to hang on some kind of wire or track or something.
教授提到这个材料也是阻止这一想法成为可能的阻碍。可喜的是目前有一种又轻又坚固的新型材料可以做到，那就是纳米管：Uh, true. And for decades that’s exactly what’s prevented the idea from being feasible or even just taken seriously. Where do we find the material strong enough yet lightweight enough to act as a cable or track?
这里*遍提到了36,000 kilometers 这个数字，教授说I mean, we are talking 36,000 kilometers here. And the strain on the cablewould be more than most materials could bear.
But a new material developed recently has a tensile strength higher than diamond, yet it’s much more flexible. I am talking about carbon nanotubes.
学生又质疑了纳米管是不是靠谱：OK. I’ve read something about carbon nanotubes.They are strong, all right, but aren’t they just very short little cylinders in shape?
教授说： Ah, yes. But these cylinders cling together at a molecular level. You pull out one nanotube or row of nanotubes, and its neighbor’s come with it, and their neighbors, and so on. So you could actually draw out a 36,000-kilometer strand or ribbon of nanotubes stronger than steel, but maybe a thousandth the thickness of a human hair. 在这个部分教授第二遍提到36,000-kilometer这个数字。
解决了材料的问题，电梯还需要一个支撑点啊，所以学生问到: OK. Fine. But what’s going to hold this ribbon up and keep it reach enough to support an elevator car?
教授回答说电梯是肯定需要定住两端的: Well, we definitely have to anchor it at both ends. So what we need is a really tall tower here on the ground right at the equator and a satellite ingeostationary orbit around the Earth. There’s a reason I mentioned that figure of 36,000 kilometers. 这里第三遍提到36,000 kilometers这个数字，因为我们需要在赤道附近建一个塔并且将另一端固定在一个和地球自转相对静止的卫星上，而这也是教授为什么会提到36,000 kilometers.这个数字的原因，所以在文中36,000 kilometers.这个数字出现了三遍，There’s a reason 是表示因果的信号词，相信这两点足以让我们引起重视啦。该题的答案应该是 satellite orbiting at this height can remain directly above on location on Earth.
What does the professor imply about the researchers’ reaction to the biological community discovered on the ocean floor?
A. They were surprised at the large variety of organisms living near hydrothermal vents.
B. They were surprised to find any bacteria living without sunlight.
C. They were disappointed at not finding any animal life.
D. They could not agree on the significance of the data that they collected.
题干中没有直接提到数字，在文中也没有反复提及数字，只是在学生问教授他们真的在这样的环境下找到了生物？So you are telling us they did find organisms that could live under thoseconditions?
教授回答：They did indeed, something like 300 different species，也就是说他们不但发现了生命还发现了多达300种，在文中这个300是有重读的。所以该题的答案应该是A,They were surprised at the large variety of organisms living near hydrothermal vents.他们惊讶竟然在热液喷口发现了大量的生物。