What is the lecture mainly about?
A.Method s of observing unusual animal behavior.
B.A theory about ways birds attract mates.
C.Ways animals behave when they have conflicting drives.
D.Criteria for classifying animal behaviors.
非常明显，答案应该是选择C选项。所以对文章结构有了一定的了解，解题就会变的非常轻松，即使文章的例子没有听懂我们也能轻松地解题。
类比开头可以分为两种，种是正比，即比较两种相同之处;第二种是反比，即比较两者不同之处。这两种都可以通过信号词判断，正比可以通过like,same等信号词判断，而反比可以通过opposite,contrast进行判断。首先我们得明白，类比开头并不能做出主旨题，不能轻易从开头做主旨，但是类比开头并不能忽略，能帮我们解决第二题，即第二题细节题，所以也不能忽视。我们来看一个例子：TPO21，Lecture 1
All right,so now we’ve talked about folk legends and seen that their...one of their key features is there’s usually some real history behind them.They are often about real people,so you can identify with the characters,and that’s what engages us in them.The particular stories might not be true and some of the characters or events might be made up.But there’s still a sense that the story could have been true since it is about a real person.That’s distinct contrast from the other main branch of popular storytelling,which is folk tales.
Folk tales are imaginative stories that...um...like folk legends,they have been passed down orally,from storyteller to storyteller for...since ancient times.But with folk tales you don’t ever really get the sense that the story might have been true.They are purely imaginative and so quite revealing,I think anyway,about the culture and the connection between folk tales and culture
从这段文章里我们看出文章是类比的开头，并且通过contrast这个信号词判断出这事反比的开头，即folk legends的主要特征是real，而folk tale是imaginative，但这里值得注意的是类比的开头并不能帮助我们做出主旨题，但是我们能做出第二题，即细节题，我们先来看下题，
