TOEFL Reading: ETS-TOEFL阅读机经 - EBQY591YVW6PIT9ZL$

According to paragraph 2, Milankovitch was the first to do which of the following? A. Introduce the idea that periodic changes in Earth's orbit could influence Earth's climate B. Show that periodic changes in Earth's orbit could be mathematically calculated C. Provide calculations to show that periodic changes in Earth's orbit could affect Earth's climate D. Propose that Earth's orbit is not fixed but undergoes periodic changes