导读： TPO (TOEFL Practice Online) 是美国教育考试服务中心(Educational Testing Service，简称ETS)专为参加托福考试TOEFL iBT(Internet-based test)，即网考托福考试的人，提供的在线模拟考试平台，考生可以实境感受TOEFL iBT考试的官方模拟试题，并即时获得考试中所测试的四种技能，阅读、听力、口语及写作的分数反馈。&nbs
TPO (TOEFL Practice Online) 是美国教育考试服务中心(Educational Testing Service，简称ETS)专为参加托福考试TOEFL iBT(Internet-based test)，即网考托福考试的人，提供的在线模拟考试平台，考生可以实境感受TOEFL iBT考试的官方模拟试题，并即时获得考试中所测试的四种技能，阅读、听力、口语及写作的分数反馈。
Starting in the 1960s and continuing until the 1980s, sailors in Russian submarines patrolling the North Atlantic and Arctic Ocean would occasionally hear strange sounds. These underwater noises reminded the submarine crews of frog croaks, so they called the sounds “quackers” (from the Russian word for frog sounds). The sources of the sound seemed to be moving with great speed and agility; however, the submarines’ sonar (a method of detecting objects underwater) was unable to detect any solid moving objects in the area. There are several theories about what might have caused the odd sounds.
The first theory suggests that the strange noises were actually the calls of male and female ocra whales during a courtship ritual. Orca whales are known to inhabit the areas where the submarines were picking up the bizarre noises. Orcas have been studied extensively, and the sounds they make when trying to attract a male are similar to those that the submarines were detecting.
A second idea is that the sounds were caused by giant squid. Giant squids are gaint marine invertebrates that live deep in the ocean and prey on large fish. They are difficult to detect by sonar because they have soft bodies with no skeleton. Not much is known about giant squid behavior, but their complex brains suggest they are intelligent animals. It is possible they have the ability to emit sound, and perhaps they approached the submarines out of curiosity.
A third theory suggests the Russian submarines were picking up stray sounds from some military technology, like another country’s submarines that were secretly patrolling the area. Perhaps the foreign submarines did not register on sonar because they were using a kind of technology specifically designed to make them undetectable by sonar. The strange froglike sounds may have been emitted by the foreign submarines unintentionally.
Summarize the points made in the lecture, being sure to explain how they challenge the specific theories presented in the reading passage.
阅读要点概括
1. Odd sounds were detected. And there are several theories about them.
2. The first theory suggests that the strange noises were actually the calls of male and female ocra whales during a courtship ritual.
3. A second idea is that the sounds were caused by giant squid.
4. A third theory suggests the Russian submarines were picking up stray sounds from some military technology
听力要点概括
1. Experts cite certain problems with all of the theories mentioned.
2. Orca whales mostly live near the surface of the water. The submarines typically remain deep in the ocean and should not have been able to hear the whale sounds from near the surface. Also the Orca whales would have been detected by the Russian sonar if they were nearby.
3. The sounds disappeared entirely by the 1980s. However, squid have always lived in the ocean where the submarines were patrolling and continue to live there today.
4. The sources of the sound appear to move around and change direction very quickly. Submarines cannot move or change direction that quickly. Also all submarines make some engine noise. But no such noise accompanied the quackers.
聚培训老师提醒：用TPO作为托福备考教材和练习工具，已经成为全球考生必选。由于TPO试题的权威性和实用性，SmartStudy(聚培训)组织了权威师资对TPO进行了逐套逐项逐题的详细讲读，包括题目理解，答题思路，解题步骤，答案分析和难点重点针对解析，覆盖最全面的做题逻辑，输出细致贴心的答题辅导，并以精美的课件清晰呈现。相信SmartStudy(聚培训)托福版块的“TPO逐题精讲”能有效帮助您查漏补缺，完美备考。
