The correct option is C Unstriated muscle
Contraction or relaxation of the urinary bladder is involuntary movement. When urine is formed, it is stored in the urinary bladder and its muscles are stretched. After accumulation of a certain amount of urine volume, urge of voiding is felt, as the stretched muscle send the signal to the brain. Involuntary muscles are unstriated or smooth muscles. Therefore, the correct answer is option B.