TOEFL Listening: ETS-TOEFL听力机经 - CM2WKR1FF15QX6AFP$

Why does the professor imply when he says this: A. The East Africa Rift System is much larger than previously thought. B. "East Africa Rift System" is an obvious name for the system. C. The East Africa Rift System is not actually a system. D. Not all of the East Africa Rift System is located in Africa.