1. **State the problem:** Calculate the total therapy time if each session lasts 50 minutes, the patient attends 3 sessions per week, and the therapy lasts for 4 weeks. 2. **Formula:** Total time = (session duration) \times (sessions per week) \times (number of weeks) 3. **Substitute values:** Total time = $50 \times 3 \times 4$ 4. **Calculate:** $50 \times 3 = 150$ 5. **Calculate:** $150 \times 4 = 600$ 6. **Answer:** The total therapy time is 600 minutes. Therefore, the correct choice is C. 600 min.