Which scenario best represents a case study?

The scenario that best represents a case study involves the in-depth analysis of a single individual or entity, which is precisely what is described in the option concerning the analysis of a single customer's donut consumption. Case studies focus on detailed and comprehensive examinations of a particular subject, providing insights into its context, challenges, and behavior over time.

In this instance, the exploration of one customer's eating habits allows for an intricate understanding of their preferences, motivations, and any unique factors influencing their consumption. This concentrated approach contrasts with broader methodologies that aim to gather information from multiple subjects or draw general conclusions from larger populations, which is characteristic of surveys or experimental studies. The nature of the analysis is qualitative, delving into the specifics of the case rather than seeking to generalize findings across a wider demographic.

The other scenarios involve methodologies that either aggregate data from numerous participants, thereby offering a more generalized perspective, or make direct comparisons between groups, which do not fit the case study model. The essence of a case study lies in its singular focus, making the analysis of one customer's donut consumption the most illustrative example of this research design.