托福听力2017年10月21日机经预测

>>托福机经：托福听力2017年10月21日机经预测

>>托福成绩提升方案

托福听力加试：

1 鸟类迁徙(conversation)

2 大王花(lecture)

3 拉格泰姆音乐(lecture)

4 女生丢 ID 卡(conversation)

5 神经胶质细胞(lecture)

6 英国浪漫主义诗歌(lecture)

7 工程队噪音(conversation)

8 16 世纪的艺术家(lecture)

9 动物社会的阶级性(lecture)

10 图书馆复印(conversation)

11 墨西哥雕塑(lecture)

12 人口和城市(lecture)

13 女生论文评语(conversation)

14 去除咖啡因(lecture)

15 营销中的 4M 理论(lecture)

16 师生讨论论文(conversation)

17 撒哈拉沙漠成因(lecture)

18 绿色产品(lecture)

C1 student & professor

C2 student & counselor

Lecture

L1 Biology

L2 Chemistry

L3 Film studies

L4 Environmental policy

Professor:

So, today we’re going to wind up our discussion of alternative energy sources and we’re going to talk about one that often gets overlooked. That source is nuclear fusion as opposed to nuclear fission, which is already discussed. In nuclear fission, the centers of atoms, the nuclei, are broken up. This is the reaction today that drives today’s nuclear-powered stadiums. Nuclear fusion, on the other hand, is pretty much the opposite. It occurs when two atoms collide and then nuclei combine, or fuse, to form a heavier nucleus. This is the reaction that powers the Sun, all stars. So, who can tell me what makes fusion more attractive than fission as an energy source. Julie?

Julie:Well, it releases more energy, for one thing.

Professor:Yeah, a lot more energy than fission.

Julie:　　Oh also, it can use hydrogen as a fuel source. And hydrogen is abundant and easily available in water. Fission uses uranium, which is way more difficult to find.

...

听力题目：

1. What is the lecture mainly about?

(A) Ways to generate heat for nuclear fusion

(B) Differences between nuclear fission and nuclear fusion

(C) A controversial theory regarding how to generate nuclear fusion

(D) The possibility of establishing sustained nuclear fusion

2. According to the students, what are three advantages of nuclear fusion over nuclear fission

Click on 3 answers.

(A) Nuclear fusion can use a fuel that is more easily obtained.

(B) Nuclear fusion can be achieved at lower temperatures.

(C) Nuclear fusion produces more energy.

(D) Nuclear fusion does not produce hazardous by-products.

(E) Nuclear fusion does not require as many natural resources.

3. Why does the professor mention isotopes of hydrogen?

(A) To correct a student's comment about how fusion takes place in stars

(B) To help answer a student's question about temperature requirements for fusion reactors

(C) To explain what happens to hydrogen atoms during fusion reactions

(D) To justify the need for superconducting magnets in nuclear fusion reactors

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