Which of the following is NOT an advantage associated with hydroelectric dams?

A) the amount of electricity can be changed rapidly
B) there are no emissions of greenhouse gases or toxic contaminants
C) the dam traps sediment that otherwise would be transported down the river
D) the main source of energy, gravity, is free

Hydroelectric Dams

Structures built across rivers to control water flow and generate electricity through the movement of water through turbines.

Greenhouse Gases

Gases in Earth's atmosphere that trap heat, including carbon dioxide and methane, contributing to global warming and climate change.

Sediment

Particles of rock, organic material, or minerals that are transported and deposited by wind, water, or ice, often forming sedimentary layers.