In the TADS Experiment, Described in the Text, the Researchers

In the TADS experiment, described in the text, the researchers used a double-blind procedure, meaning that

A) both the experimenters and the participants knew what group of adolescents were getting which treatment.
B) only the participants themselves knew which treatment they were receiving.
C) only the parents of the adolescents involved in the study were aware of which treatment they were receiving.
D) neither the participants nor the experimenters knew who was getting medication and who was getting a placebo.
E) only the experimenters knew who was getting medication and who was getting a placebo.