TOEFL Listening: ETS-TOEFL听力机经 - 14ZZT668W1UKQ63OP$

Why does the professor mention different wind speeds? A. To compare the efficiency of two different vertical axis turbine models B. To point out that vertical axis turbines work well in a variety of wind conditions C. To explain why propeller turbines require locations where extreme weather is common D. To argue against relying on wind power in certain regions