The correct answer is D. All of the above.
Economic problems arise because we have unlimited wants but limited resources. We can never have everything we want, so we have to make choices about how to use our limited resources to get the things we want most.
Unlimited wants: We have unlimited wants because our desires are always growing. We never seem to be satisfied with what we have. We always want more and better things.
Scarce resources: Resources are scarce because they are limited in supply. There is only so much land, water, oil, and other resources in the world. We can never have enough of these resources to satisfy all of our wants.
Alternative uses of scarce resources: Scarce resources can be used for different purposes. For example, land can be used to grow crops, build houses, or develop businesses. We have to make choices about how to use our scarce resources in the most efficient way possible.
Economic problems are a fundamental part of human existence. They will never go away completely. However, we can learn to manage economic problems more effectively by understanding their causes and by developing better ways to allocate our scarce resources.