Which of the Following Is an Example of Research Where

Which of the following is an example of research where there was potential harm to the researcher?

A) John Monahan and associates' research on violence.
B) Bruce Johnson's study of heroin users in New York where participants were gathered by word of mouth among addicts.
C) Reuter, MacCoun, and Murphy's study using probation records to identify drug dealers.
D) all of the above