Test the efficacy of vitamin c in preventing colds, army recruits are randomly assigned to one of two groups: one in which 500 mg of vitamin c is administered daily, and one in which 500 mg of a placebo is administered daily. both groups are followed to determine the number and severity of subsequent colds. what type of study design is this?
cross-sectional study
case-control study
prospective cohort study
historical prospective cohort study
clinical trial
community trial

This type of study design is

Clinical Trial

Step-by-step explanation:

It is clinical trial because in this study design a treatment is given to the individuals and then we observe this treatment. In this experiment, we are studying the effects by giving 500 mg of Vitamin and Placebo to the soldiers.It is not a cross-sectional study because this type of study is used to analyze characteristic of the population depending upon data but this study is not used for disease.It is also not a case-control study as well as prospective cohort study because case-control study is used to observe the new cases of a disease while prospective cohort study is used for determining risks or exposure factors of a disease. It is not a community trial as in which a community is under observation like a city or a country and it is also not a historical prospective cohort study because in this study type, we observe the cohorts (similar objects) with the different qualities. They are studied on the basis of these qualities.