Titanium is awkward to extract because carbon, the usual cheap reducing agent, reacts with it to form a hard carbide instead of freeing clean metal, so a different reductant is needed. Magnesium fills that role: titanium ore is first chlorinated into volatile titanium tetrachloride, which is purified by distillation, and this vapour is then reduced by molten magnesium under an inert argon blanket to leave a spongy mass of titanium metal along with magnesium chloride. Hall's process belongs to aluminium, Bayer's to alumina purification, and Mond's to nickel carbonyl refining, none of which apply here. So the process used for titanium is the Kroll process, option (A).