Researchers Are Conducting a Study to Determine the Effects of Vitamin

Researchers are conducting a study to determine the effects of vitamin D on the human body.The study involves providing pills that contain vitamin D to one group of human subjects and pills that do not contain the vitamin or other active ingredients to another group of people.The pills that do not contain vitamin D are

A) placebos.
B) antidotes.
C) distractors.
D) interventions.