Which of the Following Factors Would Most Severely Reduce the Usefulness

Multiple Choice

Which of the following factors would most severely reduce the usefulness of a placebo in a controlled experiment?

A) It is likely that the treatment being tested is actually no more effective than the placebo.
B) It is relatively easy for subjects to distinguish the placebo from a potentially effective treatment.
C) Some of the test subjects exhibit effects from the placebo similar to those of the treatment being tested.
D) The test subjects have not been told what effects the tested treatment would have that the placebo lacks.