Which of the following scenarios exemplifies the keeping of confidentiality?

Which of the following scenarios exemplifies the keeping of confidentiality?
A) A researcher destroys her data five years after her study is completed
B) A researcher redacts the names of participants from interview transcripts before donating them to a public library
C) A researcher quantifies participants’ individual survey responses and publishes the statistical means of her sample’s responses to each survey question
D) A researcher assigns a random number to each interviewee and uses these numbers, rather than participants’ names, to label interview recordings
E) A researcher convenes a focus group and asks the participants to share no more than their first names with one another