The answer is a. Case Study
A case study is a research methodology that involves an in-depth, detailed examination of a single subject, such as a person, group, event, or phenomenon. It is often used to gather comprehensive data and insights, allowing researchers to explore the complexities and unique aspects of the subject in question.
Natural observation involves observing subjects in their natural environment without interference or manipulation. While it provides valuable insights into behavior and interactions, it does not focus on a single subject in the detailed manner that a case study does.
Laboratory observation involves studying subjects in a controlled environment where variables can be manipulated. This method is more about testing hypotheses under controlled conditions rather than providing a comprehensive description of a single subject.
A survey is a research method used to collect data from a large number of respondents through questionnaires or interviews. It is designed to gather information on attitudes, opinions, behaviors, or characteristics of a group, rather than focusing on a single subject in depth.