选项A 给出HIV -1存在于中非猿猴的基因中，而录音中说的是最早发现感染这种病毒的是中非猿猴（ virus affecting monkeys and apes in central Africa) ，这里并 没有提及和基因有关，所以排除。选项B 为正确答案，与录音中originating from apes 意思相同。选项C 说这种病毒不能在人类身上快速、广泛传播，但录音原话是Only one form of HIV-1 has spread far and wide after jumping to humans, 即只有一种 HIV-1 病毒自从突然传染给人类后快速、广泛传播，所以也不是正确选择。选项D 根据常 识即可排除，而录音中提到90%的话是More than 90 percent of human HIV infections belong in Group M，百分比说的是感染病例，与选项无关，所以也不正确。

[重点难点]
注意把握关键性词语的含义，即此处的apes in central Africa和谈及HIV 时所用的affecting —词。

[录音原文]
Passage One
HIV began as a virus affecting monkeys and apes in central Africa. HIV, originating from apes, typically belongs to a type of virus called HIV-1. Only one form of HIV -1 has spread far and wide after jum ping to humans. This version is called HIV-1 Group M. More than 90 percent of human HIV infections belong in Group M.
What's so special about this group? Researchers from Oxford University looked at HTV genom es collected from about 800 infected people from central Africa. Genomes pick up new mutations at a fairly steady rate, so by comparing two genome sequences and counting the differences, they could work out when the two last shared a common ancestor.
They found HIV viruses evolve approximately 1 million times faster than hum an DNA. Thus, HIV-1 Group M genomes all shared a common ancestor that existed no more than 100 years ago. Because they knew where each of the 800 HIV samples had been collected, they conclude that the Group M pandemic probably first began in the 1920s in Kinshasa, capital of today's Democratic Republic of Congo.
At this point, the researchers turned to historical records. In the third decade of the 20th century, Kinshasa had just become Capital of the Belgian colony of Congo, attractive for young working men seeking their fortunes， and for sex workers only too willing to help them spend their earnings. The virus spread quickly through the population. Taking full advantage of the most extensive rail network that Kinshasa enjoyed in Africa, the virus spread to cities 1,500 kilometers away in just 20 years.
Congo gained independence in 1960, and it became an attractive source of employment to French speakers, including Haiti. Young Haitians returned home with a particular form of HIV-1 Group M to the western side of the Atlantic. It arrived in the U.S. in the 1970s, just as sexual liberation led to concentrations of gay men in cosmopolitan cities. Sociopolitical situations helped HTV spread quickly through the U.S. and Europe.

此题难度主要在于考题所问的关键词语trace HIV-1 Group M development并没有在录音中直接体现，但是录音在出现Oxford University researchers之后也用了 与考题选项一致的by comparing这个短语，所以可以根据这一共同点选择D。选项 A 所说只是如何追溯的第一步而不是关键。选项B 中 counting的对象在录音中并非 基因组（genome)本身，而是其间的差异，因此也可以排除。选项C 说科学家操纵了变异，而录音中说的是自发的变异（Genomes pick up new mutations...)，因此也不正确。

[重点难点]
抓住与问题How...相关的关键词，识别细节差异。

此题难度主要在于录音中没有用与问题中的措辞直接对应的first, transmitted to humans,答题除了注意时间词以外，从技巧上来说首先考虑使用排除法。选项A 和选项D 可以排除，因为录音中虽然说到了 one million和 800这个数字，但说的分别是 HIV 病毒演化的速度和感染病毒者人数亦即病毒样本的数量（ HIV viruses evolve approximately 1 million times faster than human DNA； about 800 infected people, 800 HIV samples)，而不是时间。正确的选项只能是B (100多年前）或 C (大约 100年），录音原话是no more than 100 years ago ,所以排除B 而确定C 为正确答案。

[重点难点]
抓住数字词及其相关关键词，注意肯定与否定的表达。

此题与录音内容一致使用了 in the third decade of the 20th century, 这对集中 注意力听取关键信息很有帮助，所以不属于难题。选项A 错，因为录音内容在给出 时间之后明确说明Kinshasa是比利时殖民地而非法国殖民地。选项B 错，因为录音根本没有提及奴隶在该地区的情况。选项C 为正确答案，这从所听到的Capital这 个词和the most extensive rail network这个词组可以判断。选项D 也应该排除，因为录音原话说到1 500这个数字时说的是病毒传播到的城市与Kinshasa之间的距离 (the vims spread to cities 1,500 kilometers away) , 而不是 Kinshasa 的面积。

[重点难点]
排除无关词语，抓住关键词语之间的关系，即railway network hub与 the most extensive rail network二者.的关系。主要难度在于理解hub这个单音节词。

选项A 给出的只是录音中解释的时代背景，与吸引年轻人没有直接的或重要 的关联。选项B 为正确答案，录音原话虽然没有与问题同样使用Haitians这个词， 但有Haiti这个词，而且同时使用了 employment这个关键词（ it became an attractive source of employment to French speakers, including Haiti) ，所以只要听懂 Haitian 就是 Haiti的变化形式，指海地人，就可以做出判断。选项C 和 D 所给的关于地理上 的远近和性自由方面的内容在录音中没有相关信息，可以排除。

[重点难点]
根据细节相关性排除干扰，抓住词性变化（Haitians与 Haiti) 与关联词 (job 与 employment) 。