Answer:
The fossil fuels are the source that supplies the majority of the world's energy.
Step-by-step explanation:
A is correct because the fossil fuels are by far the biggest energy source globally, and even though there is a gradual drop in their usage, none of the other sources produces anywhere near to be considered their competition at the moment.
B is not correct because the wind power simply doesn't have that much potential, and it is actually better for local use and small scale production of energy.
C is not correct because the geothermal energy is primarily used for other purposes, with the production of energy being minimal.
D is not correct because the solar energy is still very far away from the production of energy that the fossil fuels have, but it has to be noted that this is an energy source that actually does have the potential to compete and even replace them in the future.