An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.

　　(一个总结性句子已经给出.通过选择三个选项来完成这个总结，所选的选项需要表达原文最重要的信息.有些选项不属于总结性选项，因为他们表达了没在原文中出现的信息或者是原文中的细节信息.此题两分.)通过分析题干给出的具体信息，我们能够看出，这道题目的关键要求在于选择重要信息，总结性信息.也就意味着，有的选项虽然正确，但是如果它表达的是原文中的细节信息，那么依然不能作为正确答案，这是这道题目中最难的一个点.

　　13-14. Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas that are not presented in the passage or are minor ideas in the passage.

　　This question is worth 2 points. This passage discusses fossils that help to explain the likely origins of cetaceanswhales, porpoises, and dolphins.

　　Answer Choices

　　1. Recent discoveries of fossils have helped to show the link between land mammals and cetaceans.

　　2. The discovery of Ambulocetus natans provided evidence for a whale that lived both on land and at sea.

　　3. The skeleton of Basilosaurus was found in what had been the Tethys Sea, an area rich in fossil evidence.

　　4. Pakicetus is the oldest fossil whale yet to be found.

　　5. Fossils thought to be transitional forms between walking mammals and swimming whales were found.

　　6. Ambulocetus' hind legs were used for propulsion in the water.

　　这是每篇文章最后的一个大题，基于全文的基础进行提问，所以，我们可以根据文章的关键句，先来判断这篇文章的主要内容.以下摘选了文章的每个自然段的关键句，我们一起

　　来看一下：

　　THE ORIGINS OF CETACEANS

　　第一自然段：It should be obvious that cetaceanswhales, porpoises, and dolphins-are mammals. They breathe through lungs, not through gills, and give birth to live young. …

　　第二自然段：Very exciting discoveries have finally__ allowed scientists to reconstruct the most likely origins of cetaceans. …

　　第三自然段：The fossil consists of a complete skull of an archaeocyte, an extinct group of ancestors of modern cetaceans. Although limited to a skull, the Pakicetus fossil provides precious details on the origins of cetaceans. …

　　第四自然段：Another major discovery was made in Egypt in 1989. Several skeletons of another early whale, Basilosaurus, were found in sediments left by the Tethys Sea and now exposed in the Sahara desert. …

　　第五自然段：An even more exciting find was reported in 1994, also from Pakistan. The now extinct whale Ambulocetus natans ("the walking whale that swam") lived in the Tethys Sea 49 million years ago. …

　　首先，第一自然段综述关于鲸类动物是哺乳动物的事实，到了第二自然段开始揭示鲸类动物起源的具体细节，说到科学家有一些重要发现，到了第三自然段开始交待第一种化石的名称Pakicetus.第四自然段又提到另外一种化石发现，名字为Basilosaurus，最后一自然段提到第三种化石发现Ambulocetus natans，总结来说，这篇文章通过介绍三个化石来揭示了鲸类的起源.

　　接下来，我们来看以下选项，首先来看第一个选项：

　　1. Recent discoveries of fossils have helped to show the link between land mammals and cetaceans.( 最近的化石发现帮助解释了陆生哺乳动物与鲸类之间的关系)，此选项概括了本文的主要信息，因此可以算作小结题的答案.2. The discovery of Ambulocetus natans provided evidence for a whale that lived both on land and at sea.( 化石Ambulocetus natans 的发现提供了关于鲸及生活在陆地上又生活在海里的依据)，Ambulocetus natans 是本文三个重要化石之一， 且在本选项中体现了Ambulocetus natans 化石对于揭示鲸类起源的重要作用，因此算作小总结信息从而作为正确选项.3. The skeleton of Basilosaurus was found in what had been the Tethys Sea, an area rich in fossil evidence.(Basilosaurus 在一个叫做Tethys Sea 的地方被发现，这个地方有很多的化石)，此选项中虽然提到了本文的一个重要化石Basilosaurus，但是并没有陈述Basilosaurus 对于揭示鲸类起源的作用，因此不能算作正确答案.换句话说，只提到Basilosaurus 化石所发现的地点是不足以作为本文的小结信息的.4. Pakicetus is the oldest fossil whale yet to be found.(Pakicetus 是迄今为止发现的最古老的鲸类化石)，此选项也提到了本文中重要化石Pakicetus，但并没有提到Pakicetus 对于揭示鲸类起源的作用，因此不能作为小结题的重要选项.5. Fossils thought to be transitional forms between

　　walking mammals and swimming whales were found.(被认为是陆生哺乳动物与水生鲸类之间的过渡化石被发现)，此选项概括了本文的主要内容，本文的主旨内容即是讲述鲸类原本是陆生哺乳动物的事实，因此，5 是正确选项.6. Ambulocetus' hind legs were used for propulsion in the water.(Ambulocetus natans 的后腿用来在水中前进)，本选项貌似也提到了重要化石Ambulocetus natans，但是Ambulocetus natans 的后腿用来在水中前进是一个细节信息，因此不能作为正确答案.所以，本题的正确答案为125.