A Professor Doing Research on Deviant Behavior Asks the Students

A professor doing research on deviant behavior asks the students in her classes to fill out an anonymous self-report questionnaire dealing with their use of alcohol and nonprescription drugs. In what way is this study ethically problematic?

A) Studies of immoral behavior are inherently unethical.
B) Anonymity may not be sufficient to protect privacy.
C) Authorities may find out the names of the drug users and report them to the police.
D) Participation is not voluntary.