Which of These Situations Describes a Reactive (Hawthorne) Effect

Which of these situations describes a reactive (Hawthorne) effect?

A) Control subjects in an intervention study to reduce anxiety also experience a reduction in anxiety.
B) The subjects in an intervention support group continue the support group after the study has ended.
C) Subjects become concerned after learning that they received a placebo, not the treatment, during the study.
D) Study subjects want to know the outcomes of the study after it is completed.