Economics is the study of how individuals and societies allocate __________ resources among many competing uses.

The correct answer is 'scarce' because economics fundamentally focuses on the ways in which individuals and societies confront the problem of scarcity. Scarcity refers to the condition where human wants exceed the available resources, which means that resources are limited in comparison to the infinite desires of individuals and society. Therefore, a key component of economic study is how these limited (or scarce) resources are distributed among various competing uses. This includes decisions regarding production, consumption, and distribution in the face of finite resources.

Natural, renewable, and physical resources are specific types of resources that can be scarce; however, they are not synonymous with the fundamental concept of scarcity that's central to all economic theory. Economics applies to all forms of resources—human resources, capital, and time—when discussing how they are allocated due to scarcity. Thus, the term 'scarce' encapsulates the broadest and most fundamental concern of economics.