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

Placebos

Explanation:

Placebos are inactive treatment or substance that has no real active ingredient or pharmacological effect as that of the real treatment or substance. Participants of the experiment or drug trial that are given placebos are used as the control group. Placebos are very important in testing of new drugs. These inert substance, such as the pills that do not contain vitamin C, are often designed to look and taste exactly like that of the actual pills of the active ingredient, which is vitamin C pills in this case.

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