In the 1970s, a 13-Year-Old Girl Was Found Locked Up

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) a representative sample.
C) a single-blind study.
D) a naturalistic observation.
E) correlational examination.