TOEFL Listening: TPO-TOEFL阅读TPO - 8C9Y54DI9248LN1YN$

What is the author's primary purpose in paragraph 3? A. To explain why researchers must conduct more than one type of study when they are attempting to understand infant perception B. To describe new techniques for observing infant perception that overcome problems identified in the previous paragraph C. To present and evaluate the conclusions of various studies on infant perception D. To point out the strengths and weaknesses of three new methods for quantifying an infant's reaction to stimuli