TOEFL Listening: ETS-TOEFL听力机经 - J8_9E1UCFP5FO38WP$

What does the professor imply about rainforest destruction and pollution when says this: A. They require more research in order to be better understood. B. They will not be the focus of the class lesson. C. They are serious problems that are often ignored. D. They are very similar to processes that happened billions of years ago.