.............................Correct.
Biologists call those groups DOMAINS
Simple, we are learning about new things every day we as a human race learn something new about our world
Alternative energy sources are those that do not deplete natural resources and do not harm the environment.
Options A, B, and C are all fossil fuels, which we know can be depleted and harm the environment.
The only valid option here is D, Geothermal energy.
Geothermal energy is both renewable and environmentally friendly.