Why Do Many Environmental Groups Oppose Building More Hydroelectric Dams

Multiple Choice

Why do many environmental groups oppose building more hydroelectric dams when these dams produce virtually no chemical pollutants as they create electric power?

A) Because they increase the rate of evaporation, hence more fresh water is lost.
B) Because these dams are very expensive to build.
C) Environmental groups tend to reject all new technological advancements.
D) Dams can radically alter ecosystems.