Why Are Secondary Data Analyses Relatively Free from Ethical Problems

Why are secondary data analyses relatively free from ethical problems?

A) The data on which they are based aren't available to researchers until all study participants are deceased.
B) The research findings they generate aren't presented or published in public arenas.
C) The large samples used in this kind of research allow for anonymity on the part of subjects.
D) The researcher doesn't actually collect any data.
E) The researcher isn't aware of where or when the data were collected.