Final answer:
The psychologist would most likely use a case study to understand a client's extreme behavior. This method provides a detailed analysis of an individual but may be limited in generalizability to the broader population. So the correct answer is option (C).
Step-by-step explanation:
In order to understand a client's extreme behavior through an in-depth investigation of the client's personal and medical history, the psychologist is most likely to use a case study. A case study is a research method that entails an in-depth analysis of a single individual or event. This approach allows psychologists to collect detailed information and offers rich insights into the client's psychological makeup, behaviors, and experiences.
Case studies are particularly useful for gathering detailed information about unique or extreme cases that may not be suitable for other research methods, such as experiments or surveys. However, they are less useful for making generalizations about the broader population because they focus on one specific individual or situation.
The developmental psychologists who use this method often seek a comprehensive understanding of the psychological and physical changes over a person's lifespan. Despite providing substantial detail, it is important to acknowledge this method's limitations, such as the susceptibility to researcher bias and the difficulty in generalizing findings to a wider population.