In the 1970s, a 13-year-old girl was found locked up in a room, strapped to a potty chair. Since she had grown up in a world without human speech, researchers studied "Genie's" ability to acquire words, grammar, and pronunciation. This type of research is called a .a. case study b. representative sample c. single-blind study d. naturalistic observation

case study research

Explanation:

Case study is mostly done in social sciences in which one person, group or event is target for in-depth study. In case study mostly real-life context is studying and researcher try to explore these real-life context with help of case study. Like in this example a 13-year old locked up and studied its ability of language is case study.