You are answering a USMLE-style medical question. Question: An otherwise healthy 29-year-old man presents to his family physician with a slowly growing left neck mass for the past 5 weeks. He denies fever or recent upper respiratory tract infections. His temperature is 37.1°C (98.7°F), the blood pressure is 115/72 mm Hg, and the pulse are 82/min. On examination, a 4-cm (1.5 in), firm, non-tender mass is detected on the mid-left neck. Excisional biopsy of the mass reveals Hodgkin’s cells. The patient is referred to the oncology department and chemotherapy is started. After the first cycle of chemotherapy, the patient notices that his urine becomes red. The urine tests are positive for blood on further analysis. Which of the following is the most likely cause of this patient condition? Options: A) Bleomycin B) Cyclophosphamide C) Doxorubicin D) Etoposide Reply with ONLY the letter of the correct answer (A, B, C, or D). No explanation.