Researchers Are Conducting a Study to Determine the Effects of Vitamin

Multiple Choice

Researchers are conducting a study to determine the effects of vitamin D supplements on the adult human immune system.The study involves providing pills that contain vitamin D to one group of human adults and pills that do not contain the vitamin or other active ingredients to another group of adults.The pills that do not contain vitamin D are

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