**Core Concept**
Sociology is a social science that deals with the systematic study of human social behavior, relationships, and institutions. It examines the complexities of human interaction, social structures, and cultural norms that shape individual and collective behavior.

**Why the Correct Answer is Right**
Sociology indeed encompasses the study of both human relationships and behavior. It delves into the dynamics of social interactions, including interpersonal relationships, group dynamics, and social networks. Furthermore, sociology investigates the factors that influence human behavior, such as social norms, values, and cultural practices. By analyzing these aspects, sociologists can understand how individuals and groups interact, adapt, and change over time.

**Why Each Wrong Option is Incorrect**
**Option A:** While sociology does involve the study of human relationships, it is not limited to this aspect alone. Therefore, option A is an incomplete representation of the field.
**Option B:** Similarly, sociology does examine behavior, but it is not solely focused on this aspect. Option B is also an oversimplification of the discipline.
**Option D:** This option is incorrect because sociology does indeed study both human relationships and behavior.

**Clinical Pearl / High-Yield Fact**
A key concept in sociology is the idea of social determinants of health, which highlights the significant impact of social and economic factors on individual and population health outcomes. Understanding these determinants is crucial for developing effective public health interventions and policies.

**✓ Correct Answer: C. Both**