Researchers Are Conducting a Study to Determine the Effects of Zinc

Multiple Choice

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

A) antidotes.
B) supplements.
C) probiotics.
D) placebos.