四六级

　　英语六级听力改革后，考试题型变化较大，包括长对话、听力篇章和讲座，大家平时要有针对性的加强练习。本文是小编为大家提供的大学英语六级听力训练：mp3音频在线听第3套讲座3，希望对大家更好地进行2017年6月英语六级备考有帮助。

大学英语六级听力训练：mp3音频在线听第3套讲座3.mp3

　　Now listen to the following recording and answer questions 23 to 25

　　23

　　A.The former is helpful while the latter is harmful.

　　B.The former can be avoided while the latter cannot.

　　C.The former causes more harm than the latter.

　　D.The former is natural while the latter is not.

　　24

　　A.Large areas of forests are felled.

　　B.The world population keeps increasing.

　　C.People create things that release extra heat.

　　D.There are too many cars that bum gas.

　　25

　　A.The polar ice caps and glaciers will melt.

　　B.More animals will have to find new habitats.

　　C.The price of gas will keep soaring.

　　D.There will be more earthquakes.

　　Many people may not realize it, but the greenhouse effect and global warming are totally different things. The greenhouse effect is something that happens with all celestial bodies — planets, moons, and such—that have an atmosphere. Anyway, back to the greenhouse effect. The greenhouse effect is a process that happens when the sun's heat enters Earth's atmosphere. The sun's rays warm the earth, and the atmosphere keeps the heat in, just like a greenhouse. It's a very natural thing, and in most cases, the planet system knows how to balance itself out. Anyway, like I said, it's a pretty natural process.

　　Now all this gets messed up when humans, um, add stuff to Earth's atmosphere. That's when global warming, which is not a natural process, happens. See, what happens is that people create, um, things that create extra heat. For example, cars. We drive cars all the time. So we drive our cars, and our cars bum gas, and this exhaust is pretty hot. And the atmosphere keeps this heat around the planet. Plus, all of our machinery and our factories and stuff, they all produce heat. So all this stuff creates what scientists are calling global warming. Earth's surface and atmosphere just keep getting hotter.

　　Now global warming has many negative effects, but I think one of the biggest problems with global warming is the melting of polar ice caps and glaciers. See, our planet has huge chunks of ice at both of its poles. And when global warming happens, um, the overall temperature of the planet increases. And what this does is it makes polar ice melt. So when ice melts, it turns into water, which goes into our oceans. And that causes the level of water to rise. And this could also cause major flooding.

　　Question 23. What's the difference between greenhouse effect and global warming?

　　Question 24. According to the speaker, why does global warming happen?

　　Question 25. What's the speaker's biggest concern with global warming?

　　参考答案：

　　【小题23】D

　　【小题24】C

　　【小题25】A

　　习题解析：

　　【小题23】听力原文在对温室效应进行解释说明之后总结说Anyway, like I said, it's a pretty natural process. 指出温室效应是一个十分自然的过程。随后说到人类在大气中增加了很多物质时，所有的这一切就变糟糕了，并紧接着提到That's when global warming, which is not a natural process, happens.由此可见，全球变暖不是自然过程，而是人类使然，因此D项表述正确，故选D。

　　【小题24】听力原文中在说到全球变暖并非自然过程之后，提到See, what happens is that people create, um, things that create extra heat.由此可知，全球变暖是由于人们制造了很多排放多余热量的事物，故选C。A、B两项在听力原文中并未提及，D项中提到了消耗汽油的汽车，但这只是造成全球变暖的一个因素，并不能概括所有因素，故排除。

　　【小题25】听力原文中提到Now global warming has many negative effects, but I think one of the biggest problems with global warming is the melting of polar ice caps and glaciers.指出在演讲者看来，全球变暖的最大问题在于极地冰雪融化，因而A项表述正确，故选A。其他几项在听力原文中并未提及，均排除。

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