Your Environmental Science Instructor Tells Your Class That You Will

Your environmental science instructor tells your class that you will have an extra credit question on your next exam based on a talk to be given by a scholar visiting campus to present his research on alternative energy sources.The night before the talk,you pull an all-nighter writing a research report.You attend the talk but immediately doze off.Afterward,all you remember about the talk is that the speaker said something about working with turbines.On your next environmental science exam,your instructor asks you about the focus of the speaker's research,with the following answer choices.Which one is most likely to be the correct answer?

A) Concentrated solar thermal systems
B) Photovoltaic systems
C) Biodiesel production
D) Geothermal heat pumps