What Is Not an Advantage to Using Unstructured Interviewing Techniques

What is not an advantage to using unstructured interviewing techniques when conducting field research?

A) good when the researcher does not know much about the subject under study
B) good when the researcher may be likely to enter into casual conversation with the subject as a means of gathering data
C) good when there is a high likelihood of the subjects and the researcher spending a lot of time together
D) being able to ask pre-established questions and record the answers