Select the best definition of Broca area.

A. The motor nerve to the diaphragm, arising mainly from cervical roots C3 to C5. B. A dominant frontal-lobe region important for motor speech production. C. An arterial anastomotic ring at the base of the brain connecting anterior and posterior circulations. D. A normal narrowing where the ureter enters the urinary bladder and a common site of stone impaction.