The correct answer is D. All of the above.
Scarcity of resources is a fundamental economic problem. There are not enough resources to satisfy all human wants. This means that people must make choices about how to use their resources.
Alternative uses is another cause of economic problems. Resources can be used for many different purposes. For example, land can be used to grow crops, build houses, or mine for minerals. The decision of how to use land is an economic problem.
Unlimited wants is the third cause of economic problems. People have unlimited wants, but resources are limited. This means that people must always make choices about what to do with their limited resources.
In conclusion, the three causes of economic problems are scarcity of resources, alternative uses, and unlimited wants.