i believe the answer is c.
in order to urinate your urethral sphincters contract, these are two muscles used to control the exit of urine in the urinary bladder through the urethra.
(i concluded this through light research, this has not been in any of my health classes personally, so i could be incorrect.)
"what controls the release of urine from the bladder?
urethral sphincters. the urethral sphincters are two muscles used to control the exit of urine in the urinary bladder through the urethra. the two muscles are either the male or female external urethral sphincter and the internal urethral sphincter."
"does your bladder contract when you pee?
muscles of micturition: the detrusor and urethral sphincters. micturition, or urination, is the act of emptying the bladder. the detrusor muscle that surrounds the bladder contracts. the internal urethral sphincter relaxes, allowing for urine to pass out of the bladder into the urethra."