关于主旨，首先位置很固定，就是开头处和结尾处，而且有明显的主旨句型(开头处)因此，开头处跟在today后面，并且反复重复的词一定是主题词，还是以 chaffinch举例。注意下面的这段原文
由于托福听力最大的难点在于我们事先是看不到题的，所以整个托福听力对于我们来说就是一个定位的过程。
解释一下什么是定位，定位就是定位题点，判断这里会出题，我一直相信，定准百分之一百的位，至少可以做对百分之90的题。
So today we’re gonna talk about song development in birds and how—you may be surprised to know—the songs of most songbird species are learned—not completely instinctual—which is what we used to think…so I’d like to start things off today by, um, centering our discussion on the chaffinch.
The chaffinch is a type of European songbird, and we’re gonna use the chaffinch’s song development as illustrative of songbirds’ song development in general, because many other songbirds follow this same pattern, this pattern of learning songs.
看我标注红色的地方，这里是关键词，反复重复的都是song, development所以这就是本文要说的主旨。
而我刚讲的定位找AA，答案找AB就是这样一个理论
托福做题的过程，就是一个同义词改写的过程
还记得OG里面的第一个conversation么?里面的学生说
I have some quick questions about how to write up the research project I did this semester, about...climate varation.
原文中的定位词相当于是write the project
再看正确答案中的write the report
write就是我讲的AA，而project就是我说的AB，同义词替换
那么我们回头再看一下关于song development的lecture song development就是AA
而答案中的How it develops from an early age就是AB，嘿嘿，明白了吧
这是我关于这篇文章的笔记，我会按照笔记说定位方法
OK，因为我们说过了，文章开头是一定会出题的，而且song dvlp反复重复，所以第一个题点我就定在了，看到划得位置了么
第二个位置，定在了关于subsong的举例的位置，因为举例属于supporting detail看到了么baby反复重复，所以选B
23. How does the professor introduce her description of the sounds a chaffinch makes during subsong?
She contrasts the subsong of a chaffinch with the subsongs of other songbird species.
She compares the sounds a chaffinch makes to those a human baby makes.
She describes the sound of an adult chaffinch’s full song.
She reminds the class how scientists define begging ca lls.
结尾处，相当于主旨，而且重复，出题，看到我划得exposure，所以最后一题选C
20. What is the evidence for chaffinches’ having a sensitive period for song learning?
They begin to practice their song in the spring.
They do not develop full song until their second year.
They need little exposure to adult song in order to learn it.
They do not make many sounds for the first five weeks of their lives.