A study enrolled 240 participants with primary knee osteoarthritis (arthritis of the knee) to evaluate the effect of a new treatment, NIV-711, designed to reduce the knee pain for these patients. Knee pain was measured using a numerical rating scale (NRS). The NRS was measured at the beginning of the study (baseline) and at the end of the study. The researchers were primarily interested in the change in the NRS from baseline to the end of the study. Participants were randomized to receive a low dose of NIV-711 ($n=82$), a high dose of NIV-711 ($n=81$), or a treatment that appeared to be the same as the NIV-711 treatments but had no active ingredients ($n=77$). The intervention period was 12 weeks. The experimental units are the 240 participants, the treatments are (1) low dose NIV-711, (2) high dose NIV-711, (3) placebo. The outcome variable was the change in pain score from the beginning of the study (baseline) to the end of the 12-week intervention period.
Choose the appropriate diagram of the design for this experiment.