Which statement most accurately describes Phrenic nerve?

A. The motor nerve to the diaphragm, arising mainly from cervical roots C3 to C5. B. A specialized pacemaker region located near the superior vena cava in the right atrium. C. An arterial anastomotic ring at the base of the brain connecting anterior and posterior circulations. D. An oblique passage in the lower anterior abdominal wall transmitting the spermatic cord or round ligament.