Which statement most accurately describes Circle of Willis?

A. A specialized pacemaker region located near the superior vena cava in the right atrium. B. A major nerve that passes through the carpal tunnel and supplies thenar muscles and sensation to the lateral hand. C. An arterial anastomotic ring at the base of the brain connecting anterior and posterior circulations. D. The main venous channel that drains most of the myocardium into the right atrium.