Answer:
comparison-group
Explanation:
Comparison group: In an experiment, the term comparison group refers to the group of the different unit that either receives an alternative treatment or no treatment at all. The aim of an experiment to involve a comparison group is that it is being used as a source of counterfactual causal inference.
The comparison group allows the experimenter to claim about the aspects of intervention without assigning the participants randomly.
In the question above, the research design is the comparison group.