Final answer:
The instrument designed to dilate a male urethra is a dilator. Catheters, endoscopes, and forceps serve different purposes in medical procedures.
Step-by-step explanation:
The instrument used to dilate a male urethra is 3) Dilator. A catheter is not typically used for dilation; it is used to drain the bladder. An endoscope may be used for visualization inside the urethra during procedures, but it is not specifically a dilatory tool. Forceps are also not used for dilation. Urethral dilators are specialized medical tools designed specifically to gently enlarge the urethral passage.