Quoting others, Kumar $(2011)$ says the following about interviews:

Select one:

a$.$ Unstructured interviews are prevalent in quantitative research.

b$.$Any person$-$to$-$person interaction, either face to face or otherwise, between two or more individuals with a specific purpose in mind is called an interview.

c$.$In a flexible or unstructured interview, a researcher has the freedom to decide the format and content of questions to be asked of respondents.

d$.$ In a structured interview, one has to keep strictly to the questions decided beforehand $$ including their wording, sequence and the manner in which they are asked.

e$.$ One of the main advantages of the structured interview is that it provides uniform information.