TOEFL Reading: ETS-TOEFL阅读机经 - 95C5RXAD9363BJH4L$

Why does the author mention the fact that "the physiology of freshwater and marine animals is completely different"? A. To explain why Du Toit was able to determine that Mesosaurus was a freshwater reptile B. To explain why Du Toit concluded that certain fossils in rocks in Brazil and South Africa were those of the same animal C. To cast doubt on the idea that Mesosaurus could have swum from one landmass to another D. To show Du Toit determined which landmass Mesosaurus originated on