Let's match each process with the metal it is primarily associated with: Hall-Heroult process: This is a major industrial process for the primary production of aluminum (AI). It involves the electrolytic reduction of alumina (Al2O3) dissolved in molten cryolite. So, (A) Hall-Heroult process matches with (III) AI. Mond process: This process is used for the purification of nickel (Ni). Impure nickel is reacted with carbon monoxide to form volatile nickel tetracarbonyl [Ni(CO)4], which is then decomposed at a higher temperature to yield pure nickel. So, (B) Mond process matches with (IV) Ni. van-Arkel process: This process is used for the ultra-purification of metals like titanium (Ti), zirconium (Zr), and hafnium ( Hf ). The metal is converted into a volatile compound (e.g., iodide) and then decomposed to yield a very pure metal. So, (C) van-Arkel process matches with (I) Ti. Zone refining process: This method is used for obtaining highly pure metals, especially for semiconductors, by exploiting the difference in solubility of impurities in the molten and solid states of the metal. Metals like germanium (Ge), silicon (Si), gallium (Ga), and indium (In) are purified by this method. So, (D) Zone refining process matches with (II) In.