以一道题目为例：
While researching a topic, a student has taken the following notes:
· The Million Song Dataset (MSD) includes main audio features and descriptive tags for popular songs.
· Audio features include acoustic traits such as loudness and pitch intervals.
· Many algorithms use these audio features to predict a new song's popularity.
· These algorithms may fail to accurately identify main audio features of a song with varying acoustic traits.
· Algorithms based on descriptive tags that describe fixed traits such as genre are more reliable predictors of song popularity.
The student wants to explain a
disadvantage of relying on audio features to predict a song's popularity. Which choice most effectively uses relevant information from the notes to accomplish this goal?
disadvantage
A. Many popularity-predicting algorithms are based on a song's audio features, such as loudness and pitch intervals.
B. Algorithms based on audio features may misidentify the main features of a song with varying acoustic traits, making such algorithms less reliable predictors of popularity than those based on fixed traits.
C. Audio features describe acoustic traits such as pitch intervals, which may vary within a song, whereas descriptive tags describe fixed traits such as genre, which are reliable predictors of popularity.
D. The MSD's descriptive tags are reliable predictors of a song's popularity, as the traits they describe are fixed.
题目要求选出一个句子，能够最好地描述依赖声音特征做预测的劣势，参考材料是上方的5句话。
我们在训练的时候，会要求学生把选项先挡上，先思考这样一个问题：“如果你想研究某个对象的劣势，你面前放了很多篇文献，你要一个字一个字读吗？”
以及另一个问题：“当你把所有的劣势全部整理好以后，应该如何措辞，才能让读者方便理解？”从文法上来看，每句话的重点在这个句子的主干中，如果是表示评价或者后续影响的部分，可能放在逗号ing或者放在逗号which里。
把这两个问题想明白以后，按照流程操作就可以了。如果要找一个对象的劣势，一定要去文章里面找到否定或者负面的评价。在材料的五句话中，有一句话就有否定：These algorithms may fail to accurately identify main audio features of a song with varying acoustic traits. 这句话中的fail to表示没能够做成一件事。
学生在做SAT语文题的时候，除了要把句子的大意说出来，还要额外做一件事：把每个句子的功能总结出来。作者写这句话是为了什么？引入背景？陈述现象？作出解释？提出观点？提出别人的观点？评价一件事？等等。
先来看阅读材料：
The Million Song Dataset (MSD) includes main audio features and descriptive tags for popular songs.
这句话的大意是：MSD包含了主要的流行歌曲的音频特征和标签。
这句话的功能是：描述MSD的内容。
· Audio features include acoustic traits such as loudness and pitch intervals.
这句话的大意是：音频特征包括声音特征，比如响度和音程。
这句话的功能是：描述audio feature的内容。
· Many algorithms use these audio features to predict a new song's popularity.
这句话的大意是：很多算法用这些音频特征预测一首新歌会不会火。
这句话的功能是：介绍一个算法的功能。
· These algorithms may fail to accurately identify main audio features of a song with varying acoustic traits.
这句话的大意是：如果一首歌有很多声音特性的话，这些算法没法准确地识别一首歌的主要音频特征。
这句话的功能是：描述某个算法的问题。
· Algorithms based on descriptive tags that describe fixed traits such as genre are more reliable predictors of song popularity.
这句话的大意是：如果算法基于像基因这样描述固定特性的标签的话，那么这些算法就能够更靠谱地预测一首歌能不能火。
这句话的功能是：算法靠谱的条件。
我们看一下几个选项的大意和功能：
A选项：
Many popularity-predicting algorithms are based on a song's audio features, such as loudness and pitch intervals.
这句话的大意是：很多预测是否会火的算法是基于一首歌的音频特征的，比如这首歌的音量和音程。
功能：描述某个算法的依据，不涉及评价和负面描述。
B选项：
Algorithms based on audio features may misidentify the main features of a song with varying acoustic traits, making such algorithms less reliable predictors of popularity than those based on fixed traits.
这句话的大意是：基于音频特征的算法可能会错误地识别某些歌曲的主要特征，这些歌曲有很多的音频特征。这样一来，这种算法跟基于固定特征的算法相比，在预测歌曲是否会流行这方面，就不那么靠谱了。
这句话的功能是：指出某种算法的错误，并对该算法评价。
C选项：
Audio features describe acoustic traits such as pitch intervals, which may vary within a song, whereas descriptive tags describe fixed traits such as genre, which are reliable predictors of popularity.
这句话的大意是：音频特征描述的是声音的特性，比如音程，它在一首歌内会发生变化，而描述性标签描述的是固定的特征，比如体裁，它可以很靠谱地预测一首歌会不会火。
这句话的功能是：两种对象的内容作比较。
D选项：
The MSD's descriptive tags are reliable predictors of a song's popularity, as the traits they describe are fixed.
这句话的大意是：MSD的描述性标签能够很靠谱地预测一首歌能不能火，因为这些标签所描述的特征是固定的。
这句话的功能是：对标签进行正面评价，并给出解释。
四个选项中，光看内容，ABCD都或多或少有道理，但是真正能够回应题目要求的，出现了负面评价的只有B选项，它就是正确答案。
其实如果我们仔细研究SAT的考题就不难发现，无论是阅读还是语法，出题人本质想考察的并不是考生的英语能力，而是学术能力。这也是为什么那么多地区认可SAT考试的根本原因。
