In this method, a low melting metal like tin can be made to flow on a sloping surface. In this way, it is separated from higher melting impurities. The method is known as:
A. distillation
B. vapor phase refining
C. liquation
D. zone refining

Hint:Metallurgy is a process of extraction of metals from its ores. This includes several steps like concentration of the ores, production of crude metal, refining of crude metal and crushing and pulverization. Metals are refined to purify the metals. It is completely dependent on the difference between the properties and impurities of metals.

Complete step by step solution:
Now let’s explain each method one by one.
A. Distillation is based on the boiling points. This is used for volatile metals which have lower boiling points than their impurities. For example, zinc, mercury can be separated by distillation. Initially, the metal is heated to more than its boiling point. Impurities do not get vaporized, but the metal gets vaporized and condensed. Thus only the impurities are left.
B. Vapor phase refining is of two types-Van-Arkel method and Mond’s process. The Van-arkel method is to refine zirconium or titanium.
Mond’s process is used to refine nickel.
C. Liquation is used for separating metals which have lower melting points than the impurities. The process is done by keeping the metal to be refined in a sloping surface of a furnace. The temperature will be maintained above the melting point of metals. Thus the pure metal melts and moves down.
E.g. tin, lead, bismuth, mercury etc.
D. Based on the difference in the solubilities of impurities in molten state and solid state of metals, zone refining is done. Thus highly pure metals are obtained from this method. E.g. silicon, germanium etc.

Hence, option C is correct.

Note:
Pulverization is the breaking down of large pieces to small pieces. Ore concentration is the impurities removal from the crushed ore. The production of crude metal includes conversion to oxides and reduction of oxides to metals.