Professor eatwell plans to study the effect of zinc supplements on young adults' susceptibility to the cold virus. she will give some of the young adults zinc supplements while the group will get supplements that do not contain zinc.

Control

Explanation:

Professor Eatwell is trying to study the effects of zinc supplements on  young adults' susceptibility to the cold virus. In order to study the effect of zinc supplements it must be made sure that the effects observed during the study is the effect of the zinc supplement solely.

In order for this to happen a control group is used where the group is not given zinc supplements even though the group members think that they are receiving zinc supplements.

what is the question you are trying to ask?