TOEFL Listening: ETS-TOEFL听力机经 - QVY54P95OBTCCIU3P$

According to the professor, which of the following are causes of desertification? A. Communities in drylands overusing their water supplies. B. The limited supply of fresh water on Earth. C. Neglect to rotate the types of crops farmed. D. Grazing animals using more water than is sustainable.