TOEFL Listening: ETS-TOEFL听力机经 - 3TD598X8DVI0DZ1RP$

What is the main purpose of the lecture? A. To illustrate similarities between two periods of climate change B. To examine theories about the extinction of large North American mammals C. To describe how scientists verify occurrences of meteor impacts on Earth D. To present a new explanation for the cause of the end of the last ice age