Which of the following best defines a 'case study' in research methodology?

A 'case study' is defined as an in-depth investigation of an individual, group, event, or situation to provide comprehensive insights into a specific phenomenon. This methodology allows researchers to gather detailed contextual information and explore the complexities involved in the subject being studied.

In the context of research, a case study is particularly valuable because it enables a holistic understanding of the relevant factors and interrelationships that contribute to the outcomes observed. It often employs various data collection methods, such as interviews, observations, and document analysis, which can yield rich qualitative data.

By focusing on either an individual or a group, the case study approach allows researchers to explore specific contexts, patterns, and behaviors, which can then inform broader theories or practices in the field. This makes option B the best definition of a 'case study' in research methodology.

The other options involve different research approaches. Quantitative analysis requires statistical data across many subjects, which is not the focus of a case study. A literature review summarizes existing research rather than investigating an individual case, and a general survey collects opinions but does not provide the in-depth analysis that a case study entails.