Which of the Following Is an Example of Secondary Data

Which of the following is an example of secondary data?

A) Transcripts from a series of focus groups conducted for the current research problem
B) Diaries kept by panel participants who are currently evaluating their consumption of milk
C) Sales records for the past 5 years
D) Completed questionnaires from a mail survey
E) Data file from a web survey deployed as part of the current research design