The correct option is D Statement 2 explains statement 1.
Water is one of the easily available renewable energy sources on our planet, as we have most (≈70%) of our planet covered in water. It is considered a renewable source because it can easily be replenished through water cycle (evaporation & precipitation).
As it causes less to no pollution, harnessing energy from water through hydroelectric power plants or marine turbines is considerably easy and safe for the environment.
So, both the statements are correct, and the statement 2 is the explanation of the statement 1.