A Primary Difference Between a Structured Interview and an Unstructured

A primary difference between a structured interview and an unstructured interview is:

A) structured interviews may present the expected answers to the questions, whereas unstructured interviews do not.
B) unstructured interviews are conducted by a third person, whereas structured interviews are conducted by the researcher.
C) only unstructured interviews can be conducted in a phone survey.
D) good interpersonal skills are important only for the interviewer conducting an unstructured interview.