Answer:
d. improve the likelihood that the two groups will be comparable with regard to known and unknown confounding factors.
Step-by-step explanation:
Epidemiology is the term that is used to define a study in which the study is done on a defined population for the health related issues, that is about answering the who, when and where related to this study.
In this given question also the experiment focuses on developing two different groups to understand and conduct the study and analysis properly, based on the suspected factor and how they react to it.
Thus, it will lead to compare the groups in order to make the analysis efficient keeping constant factors.