TOEFL Listening: ETS-TOEFL听力机经 - 1XG4US4GQ1BQE9TCP$

Why does the professor say this: A. To emphasize how badly droughts affect the environment. B. To clarify that humans are not always the cause of soil degradation. C. To stress that desertification is a current cause for concern. D. To avoid placing blame on a particular group of people.