The fundamental economic problem is scarcity - human wants are unlimited, but the resources available to satisfy those wants are limited. Economic problems arise mainly because of these limitations in the availability of resources.
Because resources (land, labour, capital, and entrepreneurship) are scarce relative to the unlimited desires of society, choices must be made about how to allocate them. This gives rise to the three basic economic questions: what to produce, how to produce, and for whom to produce. Every choice involves an opportunity cost - the next best alternative forgone.
While lack of foresight, inaccurate data, and wastage of resources are real problems that can worsen economic outcomes, they are not the primary cause of economic problems. Even with perfect foresight, accurate statistics, and zero waste, economic problems would still exist because resources remain limited relative to wants. Scarcity is the root cause from which all other economic problems stem.
For examinations, always connect the concept of scarcity to the need for choice and opportunity cost - these three ideas form the foundation of economics.