Final answer:
The main difference is that a case study focuses on a detailed examination of a single entity, whereas surveys collect responses from many people to draw conclusions about a larger population.
Step-by-step explanation:
One difference between a case study and a survey is that a case study involves an in-depth analysis of a single event, situation, or individual, typically using various data collection methods such as interviews, observation, and document reviews. In contrast, surveys are designed to collect data from a large number of individuals asking the same questions to all respondents, which allows for data to be tabulated and interpreted on a broader scale. The depth of detail in case studies can be much greater, while surveys allow researchers to infer results to a larger population.
Given this information, the correct answer to the student's question would be: A. A case study involves one person; a survey usually involves many people. Surveys aim to extrapolate conclusions to a larger group, whereas case studies provide a detailed examination of a single case. Additionally, the nature of questioning in surveys is often more structured and less detailed than the inquiry found in a case study.