TOEFL Listening: ETS-TOEFL听力机经 - 3WZDH993NJMY3OY2P$

Why does the woman mention global warming? A. To point out a process that can't be accounted for by the Milankovitch theory B. To suggest that greenhouse gases were present in Earth's atmosphere during the last ice age C. To challenge the idea that ice ages will continue to come and go in the future D. To express her opinion that society should work harder to stop global warming