TOEFL Listening: TPO-TOEFL听力TPO - ZZD39VG0391BJ2F8R$

What did researchers notice that could be evidence of an asteroid impact in Wilkes Land? A. A ring of ice containing a high concentration of oxygen. B. A portion of Earth's crust that is less dense than normal. C. Extraterrestrial rock fragments lying below the ice. D. Relatively high gravity measurements in the center of a circular ridge.