Select the best definition of Brachial plexus.

A. A normal narrowing where the ureter enters the urinary bladder and a common site of stone impaction. B. A network of spinal nerve roots C5 to T1 that supplies the upper limb. C. The free edge of the lesser omentum containing the portal triad. D. An arterial anastomotic ring at the base of the brain connecting anterior and posterior circulations.