TOEFL Listening: ETS-TOEFL听力机经 - PA71C00H95FUPR57P$

Why does the professor mention the fossil record? A. To provide background for a topic he wants to discuss. B. To suggest that a geologic time period may have been inaccurately estimated. C. To make a distinction between speculation and hypothesis. D. To give an overview about how shelled animals become fossilized.