As a sociologist, you would be most likely to observe:

The most appropriate choice for a sociologist observing human behavior is indeed centered on the behavior of human beings in television focus groups. Sociology primarily focuses on the study of social behavior, the interactions among individuals, groups, and institutions. Observing focus groups provides insights into how people think, feel, and behave in social situations, particularly concerning media and communication. This method allows sociologists to understand collective attitudes, cultural norms, and the influence of media on social perceptions.

In contrast, the other options lean towards different fields. Observing the effects of an earthquake on farmland typically falls under environmental science or agricultural studies, focusing on ecological impacts rather than social interactions. The behavior of rats in sensory-deprivation experiments would be more relevant to psychology or biology, as it deals with animal behavior and experimental methods rather than human social behavior. Lastly, studying the change over time in Babylonian obelisk styles pertains to archaeology or art history, focusing on historical artifacts rather than contemporary human interactions.

By focusing on how individuals behave in structured social environments like focus groups, a sociologist can draw conclusions about social dynamics, making this choice the most fitting for their area of study.