Which feature of society refers to its size?

The correct answer pertains to the aspect of society that relates specifically to its size, which is captured effectively by the concept of membership count. Membership count refers to the total number of individuals in a particular social group or society, making it a direct measure of size. Understanding the size of a society can have implications on resource distribution, social dynamics, and the structure of interactions within that group.

In contrast, population density refers to the number of people living in a specific area and can vary widely even within societies of similar membership counts, thus not strictly defining the total size of a society. Autonomy pertains to the degree of independence or self-governance of a society rather than its size. Proximity generally deals with the physical closeness of groups or individuals, which also does not directly indicate the overall size of the society. This contextual understanding highlights why membership count is the most appropriate choice when addressing the size of a society.