What Is the Hawthorne Effect

What is the Hawthorne effect?

A) A reactivity effect named after a famous case in which subject responded to the fact that they were in an experiment more than to the treatment. In effect, the experiment became the independent variable.
B) It is a special instrument for measuring emotionally charged attitudes invented in the 1930s Hawthorne, England.
C) When subjects do not receive the real treatment and instead receive an imitation treatment but respond as though they have received the real treatment. In effect, the belief that they received a treatment effects their behavior.
D) It is a type of experimental design using three control groups developed by Sir Thomas Hawthorne in the 1960s when investigating the effects of noise on mental concentration.