1. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive 托福听力考前串讲（一）

2. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive 天文学 TPO26-Lecture 3

3. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive What is the lecture mainly about? A. The orbits of comets B. Unique characteristics of a famous comet C. The structure of comets D. The origin and life cycle of comets

4. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive According to the professor, what happens as a comet approaches the Sun? Click on 2 answers. A. Its nucleus loses some material B. Its core becomes brighter C. It moves faster D. It absorbs gases from the Sun

5. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive Why does the professor emphasize the amount of time Hailey’s Comet is beyond the orbit of Jupiter? A. To account for the comet’s composition of ice and dust B. To show the effect of Jupiter’s gravity on the comet’s orbit C. To argue that the comet’s orbit should not be considered periodic D. To explain why the comet is not visible from Earth very often

6. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive What is the professor imply about the history of Hailey’s Comet? A. Hailey’s Comet did not always have the same orbit it has now B. Hailey’s Comet used to be much smaller than it is now C. Hailey’s Comet has always had the same orbit that it has now D. Hailey’s Comet is much younger than the rest of the solar system

7. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive What is the professor’s opinion about the name” parabolic- orbit comets”? A. It is not widely accepted among astronomers B. It is probably not strictly accurate C. It is not a term that the students need to learn D. It will probably be replaced soon with a new name

8. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive According to the professor, what can change a parabolic-orbit into a periodic-orbit comet? A. The loss of some of the comet’s material B. The force of escaping gases C. The gravitational influence of a planet D. Energy from the Sun

9. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive 地质学 TPO16-Lecture 1

10. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive What is the main purpose of the lecture? A. To explain the various ways that sulfuric acid is involved in the formation of caves B. To describe caves and other geologic formations in U.S. national parks C. To use Lechuguilla Cave as an example of how most caves form D. To discuss the formation and characteristics of an unusual type of cave

11. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive The professor mentions parts of the process involved in the formation of Lechugilla Cave Indicate which of the statements below describe part of the process. Click in the coned box for each phrase YesNo Gypsum residue accumulated to form decorative structures Gas generated by bacteria reacted with gypsum deposits Hydrogen sulfide gas mixed with underground water Acid dissolved parts of the limestone Bacteria fed on underground oil Flowing surface water enlarged the cracks in the limestone

12. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive According to the professor, what substance found in surface water is important for the formation of typical limestone caves? A. Gypsum B. Oxygen C. Carbonic acid D. Sulfuric acid

13. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive What does the presence of gypsum in Lechuguilla Cave indicate? A. The cave was not formed by flowing water B. The cave is no longer forming C. Bacteria are present in high concentrations inside the cave D. No type of acid was involved in the formation of the cave

14. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive What can be inferred from be fact that Lechuguilla Cave is no longer forming? A. The cave has stopped attracting visitors B. The cave no longer contains any limestone C. The air in the cave is safer to breathe now than it was in the past D. Gypsum deposits inside the cave are growing thicker

15. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive What does the professor mean when he says this A. Lechuguilia Cave is not completely absent of water B. Lechuguilia Cave is not totally safe to explore C. Water long ago flowed through Lechuguilia Cave D. Scientists do not agree about how Lechuguilia Cave was formed

16. 小马公开课 400-663-1986 小马公开课网址： http://bbs.xiaoma.com/util/opencourseactive http://bbs.xiaoma.com/util/opencourseactive