An investigator seeks to evaluate the independent and combined effects of a low-sodium diet and a daily exercise program on systolic blood pressure reduction. 240 patients with essential hypertension are randomized equally into four groups for 12 weeks: Group A follows the low-sodium diet alone; Group B participates in the exercise program alone; Group C follows both the diet and exercise interventions; and Group D receives neither intervention (usual care). Blood pressure is measured at baseline and after 12 weeks. No crossovers or washout periods occur. Which study design best describes this trial?