Which of the following statements is true about hydropower?

It releases carbon dioxide.
It can produce harmful chemicals.
It can affect fish and other marine life.
It uses gas trapped under Earth's surface.

Answer C: It can affect fish and other marine life.

Explanation:

Hydropower plants can harm ecosystems, especially killing fish with their turbines.

Note: Hydropower generators do not directly emit air pollutants. However, dams, reservoirs, and the operation of hydroelectric generators can affect the environment. And greenhouse gases (GHG) such as Carbon Dioxide (MENTIONED IN ANSWER A) and methane form in natural aquatic systems and in human-made water storage reservoirs as a result of the aerobic and anaerobic decomposition of biomass in the water.

However, if we can choose just the only one answer, then the answer is C.