In order to understand the unusual behavior of an adult client, a clinical psychologist has carefully investigated the client's current life situation and his physical, social, and educational history. Which research method has the psychologist employed?

Answer: Case study

Explanation:

Case study is known to be a type of research method which aims to do a comprehensive investigation and analysis of a subject or person, situation and so on. With the use of this method, comprehensive observations can be made by researchers and it can be carried out with tools such as observations, artifacts, interviews, survey and so on. Thus, it is a research method which is popularly used by social scientists.