Write out the components of the conduction system of heart.

A． at the internal urethral orifice
B．at the external orifice of urethra
C．at the membranous part
D．at prostatic part
E．at bulb of urethra

A．common carotid a. and its branches
B．internal jugular v. and its tributaries
C．hypoglossal n.
D．vagus nerve
E．accessory nerve