TOEFL Listening: TPO-TOEFL听力TPO - 1N_5R802Q0RTQ951R$

Why does the professor say this: A. To correct misstatement he made about Sahara's climate. B. To suggest that the current dryness of Sahara is exaggerated. C. To indicate that scientists are not in agreement about the Sahara's past climate. D. To emphasize the difference between the current and past climates of the Sahara.