Correct option is B
Mitomycin requires adequate contact time with bladder mucosa. Patients are instructed to retain urine for 1–2 hours post-instillation for maximum efficacy.
Explanation of options: (a) ✘ Immediate voiding reduces therapeutic effect. (b) ✔ Correct; 1–2 hr retention improves mucosal exposure. (c) ✘ Hydration is good after therapy but not immediately. (d) ✘ Positioning for hours is not part of protocol.