Answer:
C. The treatment in the experiment must be applied to each of the individuals in the experimental group.
Explanation:
Experimental studies are the studies in which the researcher introduced the intervention and the impact of the study. It usually randomized.
Moreover, it must be applied for each and every individual in the experimental group as the variables & conditions would be vary and the same would be applied so that the actual results may be concluded
Hence, the option c is correct