听力练习材料每周一篇讲座（分为三天讲解分析）、一遍对话（分为两天讲解分析），因此每周内容在此汇总，便于回顾当周的练习内容。
每日链接汇总（文章会在任务日当天0点发出）：
另外，每周第三天、第五天会在下面发出讲座和对话的整体练习材料作为一周回顾和巩固练习的材料，同学们可在周末复习、熟悉练习过的内容。
TPO53-L4
1.What is the main purpose of the lecture?
A. To show the connection between asteroids and Saturn’s rings
B. To discuss theories about the formation of Saturn’s rings
C. To describe the composition of Saturn’s rings
D. To show how Saturn’s rings affect the planet’s atmosphere
2.What leads scientists to believe that Saturn’s rings are much younger than the planet itself?
A. Most of the rings are bright and shiny.
B. Most of the rings are composed of complex materials.
C. The rings are much thinner than scientists realized.
D. There are small moons in between Saturn’s rings.
3.Why do astronomers suspect that new material has been added to Saturn’s ring system?
A. The number of moons orbiting Saturn has increased over time.
B. The rings exist in spite of Saturn’s gravity and magnetic pull.
C. The tidal forces of Saturn are stronger than previously believed.
D. The amount of water-ice in Saturn’s rings is smaller than previously believed.
4.Why does the professor mention Edouard Roche?
A. To explain why Saturn’s magnetic pull affects the orbits of Saturn’s moons
B. To explain how much gravitational force is needed to make particles coalesce into a moon
C. To explain how a moon might contribute material to Saturn’s ring system
D. To explain why asteroids are attracted to Saturn’s ring system
5.Why does the professor mention the reddish color in some of Saturn’s rings?
A. To explain why he calls Saturn “the jewel of the solar system”
B. To prove that Saturn’s rings and its moons are composed of similar material
C. To explain how scientists realized that the ring particles vary greatly in size
D. To support the possibility that some rings may contain molecules from an asteroid
6.Why does the professor say this:
A. He wants the woman to answer her own question.
B. He wants the woman to rephrase her question.
C. He is glad that the woman understands the point he just made.
D. He believes that more research on ring formation is needed.
答案：B A B C D C