What structure is shared by the urinary system and the reproductive system in the male?

The correct answer is urethra.

In males, the urethra is a tube that connects the urinary bladder to the urinary meatus (opening) for the removal of urine from the body but it also travels through the penis and carries semen which means that is part of both, urinary and reproductive systems. Males use urethra for urination and ejaculation and thus they contain external urethral sphincter and internal urethral sphincter muscle.