Aconitum napellus is a species of flowering plant in the genus Aconitum of the family Ranunculaceae, native and endemic to western and central Europe. 'Aconite' is obtained from the dried, tuberous root of Aconitum napellus, a perennial plant abounding in the mountains of Europe and Asia. The leaves and root are both used, but the latter is the most powerful. The alkaloid 'aconitia' or 'aconitine' is a sedative poison, obtained from the root and is externally employed for neuralgic affections, producing a sensation of heat and pricking. So, option A is correct.