Which of the following is an environmental problem associated with hydroelectric power production?
a. it alters the breeding habits of fish, especially salmon
b. it creates flooding of important habits
c. it damages rivers
d. all above

D, All of the above. Hydroelectric dams basically make water go through a big turbine that make electricity. In order to do this, the company has to block off an entire section of river (which causes flooding and damages the surrounding area) and build the dam, then it prevents water from flowing freely (which disrupts breeding habits). That covers all the answers making D the only possible one.