Section: Listening Part B

38)

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Listen to the conversation and answer the question.

1. To demonstrate it's easier to digest food when it's broken down
2. To persuade the readers to chew their food longer
3. To compare iodine's reaction to different chemicals
4. To give specific directions for the experiment

(A) is the main idea of the talk.

(B) is incorrect because the author does not try to convince the reader. (C) is too general. Although the talk gives specific directions for the experiment, (D) is not the main idea.