Answer:
The correct option is : c. external sphincter muscle of the bladder
Explanation:
The process of excretion of urine from the urinary bladder to outside the body through the urethra is known as Micturition. The other names for micturition are urination and voiding.
In a normal human being, the process of micturition requires both the voluntary and involuntary nervous system components.
The external sphincter is a voluntary muscle. For urination to occur the external sphincter muscle must be relaxed.
Therefore, the process of voiding urine begins if the external sphincter muscle relaxes voluntarily.