18.在排尿(micturition)過程中,副交感神經的作用為下列何者? (A)刺激膀胱(urinary bladder)收縮 (B)刺激尿道內括約肌(internal urethral sphincter)收縮 (C)抑制腦幹(brain stem)功能 (D)使尿道外括約肌(external urethral sphincter)鬆弛