举例说明：
Professor: Through much of the last century, America’s faith in freedom and democracy was a rock in a raging sea. Now it is a seed upon the wind, taking root in many nations.
Narrator:
Listen again to a part of the lecture. Then answer the question.
Professor: …Now it is a seed upon the wind, taking root in many nations.
Why does the professor say this?
A: To encourage the students to think about the issue under a bigger context.
B: To elicit an answer from the students.
C: To compare two different things figuratively to engage his students.
D: To describe an imaginative situation.
解析：
该题是询问为何使用某种修辞手法。
从谈话节选段落中我们很容易看出，教授使用的是暗喻的方法。
该段落大概的意思是：在上个世纪的大部分时间里，美国式民主和自由的信仰如石沉大海，波澜不惊;而今，却如清风拂絮，撒落人间。
暗喻的方式是为了形成对比，从而激起听者的想象力，活跃课堂谈话的气氛。
综上所述正确答案为C。
总之，在把握托福IBT听力修辞题的时候要多多注意材料中出现的修辞方法，例如比喻，夸张，比拟，接待，反问等。排除干扰项，选出正确答案。
