A is probably wrong because gold is a type of mineral
B is probably wrong because solar power is not a resource that Earth produces, rather it is something humans extract from the Sun
C is the most likely answer because forests are classified as natural resources
D is probably wrong because farmland can be made by humans
A natural resource is a resource that cannot be made by humans. This resource is most likely difficult to reproduce. Since it takes hundreds upon hundreds of years to grow a forest, this makes it a resource only natural to the Earth that will eventually deplete itself.
