Which of the following statements is true of the role of cover letters?

A$.$ They serve as a blueprint for training people to complete the interviewing process in a consistent fashion.

They are used by interviewers in qualitative research studies.

They are designed to enhance respondents' willingness to complete surveys.

They are used for training interviewers to correctly select prospective respondents.

They are used to exclude respondents that are representative of the defined target population of a study.