A Major Advantage of Using a Coding or Linkage System

A major advantage of using a coding or linkage system to ensure the confidentiality of data on human research participants is that

A) data protected by a coding or linkage system have privileged legal status in the courts.
B) this system guarantees research participants that no one can determine how they responded to the research instruments.
C) this approach is more ethical than a completely anonymous procedure.
D) if necessary, the researcher can identify participants who failed to respond or misinterpreted the instructions.