Problem: Which one of the following patients is at the LOWEST risk for stroke? OA-A45-year-old female who smokes cigarettes and takes oral contraceptives. OB-A 30-year old Black male with sickle cell disease OC A 63-year old patient with atrial fibrillation and diabetes mellitus OD-A 35-year-old female with a deep-vein thrombosis secondary to calf injury