Raynaud's phenomenon is characterized by while thromboangiitis obliterans (buerger's disease) is characterized by of the arterial vessels in the hands and/or feet.

Raynaud's phenomenon refers to an ailment featured by blood vessel unusuality resulting due to overactivity of the smooth muscle in the wall of arteries, causing spasms (vasospasms with constriction) of the small vessels, which supply blood to the legs, arms, feet, and hands, and sometimes the nose and ears.

Thromboangiitis obliterans, also known as Buerger's disease and vasculitis, is characterized by thrombosis and inflammation of the small and medium arteries of the feet and legs that recurs and advances in phases.

the correct answer is b