【正确答案】 B

【答案解析】[听力原文] OK, last time we talked about ancient agricultural civilizations that observed the stars and then used those observations to keep track of the seasons. Today I want to talk about the importance of stars for early sailors, about how the fixed patterns of stars were used as navigational aids. OK, you've all heard about the Vikings and their impressive navigation skills, but the sailors of the pacific islands, the Polynesians and the Micronesians, were quite possibly the world's greatest navigators. Long before the development of, uh, advanced navigational tools in Europe, pacific islanders were travelling from New Zealand to Hawaii and back again, using nothing but the stars as their navigational instruments. Um, the key to the pacific islanders' success was probably their location near the equator. What that meant was that the sky could be partitioned, divided up, in symmetry than it could farther away from the equator. Unlike the Vikings, early observers of the stars in Polynesia or really anywhere along the equator would feel that they were at the very center of things. With the skies to the north and the skies to the south behaving identically, they could see stars going straight up in the east and straight down in the west. So it was easier to discern the order in the sky than farther north or farther south, where everything would seem more chaotic. Um, islanders from all over the pacific learned to use the stars for navigation, and they passed this knowledge down from generation to generation. Some of them utilized stone structures called stone canoes, ah, and these canoes were on land, of course, and you can still see them on some islands today. They were positioned as if they were heading in the direction of the points on the sea horizon where certain stars would appear and disappear during the night, and, um, young would-be navigators set by the stones at night and turned in different directions to memorize the stars they saw, so they could recognize them and navigate by them later on when they went out to sea. One important way the Polynesians had for orienting themselves was by using zenith stars. Urn, another technique used by the Polynesians was to look for a star pair, that's two stars that rise at the same time, or set at the same time. This will be discussed the next class. What we should know is that these techniques could help identify a location relative to the equator. Uh, OK, I think all this shows that navigating doesn't really require fancy navigational instruments; the peoples of the pacific islands had such expert knowledge of astronomy as well as navigation that they were able to navigate over vast stretches of Open Ocean. What does the professor mainly discuss? 本录音四道题选项中的sailing skills，navigate，stars，navigational instruments/tools和location表明，录音可能与航海有关，可能涉及航海技术或方位的确定。 四个选项均概括性较强表明，本题可能考查录音的主旨。 录音一开始便提到，今天主要讨论星星对早期船员的重要性，他们是如何利用固定的星象模式(fixed patterns of stars)来协助航海的。之后具体讨论了太平洋岛屿上的居民是如何仅靠星星来导航的。B与此表述一致，故为答案。

【正确答案】 D

【答案解析】[听力原文] What is the advantage of observing stars from a location near the equator? 选项均为含有比较结构的句子，其中重复出现的anywhere else和farther north or south，以及horizon和stars rise表明，本题可能考查某些东西在不同地方所呈现的不同之处，可能与地平线和星星有关。 录音中提到，太平洋岛上的居民之所以能成功靠星星来导航的关键很可能在于他们靠近赤道，这就意味着比起远离赤道的地方，这里的天空是对称的。D是对该信息的同义转述，故为答案。

【正确答案】 C

【答案解析】[听力原文] Why does the professor mention stone canoes? 选项均为动词不定式短语，其中的point out, give an example of, illustrate和compare表明，本题可能考查录音中提及某事的作用。 录音中教授先提出论点——太平洋盗上的所有居民都学会了使用星星来导航，这种技巧代代相传。接着谈到他们中的一些人使用石头制成的独木舟来确认航行的方向，年轻的水手进行观察学习以便以后出海时使用该技巧。由此可推知，该例子是用来支撑之前教授所提的观点，故答案为C。

【正确答案】 A

【答案解析】[听力原文] What did the technique using zenith stars have in common with the technique using star pairs? 选项中重复出现的both，以及could help identify和used to/as表明，本题可能考查某两种事物的相同作用。 录音中分别提到了波利尼西亚人利用天顶星(zenith stars)和星对(star pairs)来导航的技术，并总结提出这两种技术都可以帮助他们确定自己相对于赤道的位置(a location relative to the equator)，故答案为A。