Chemical separation is one of the methods employed in (a) dressing of ore (b) concentration of ore (c) extraction of metal from its oxide (d) conversion of ore to oxide

Dressing of ore means the process of removing unwanted materials, such as sand, clay rocks, etc., from the ore. This process uses mechanical methods like sieving, magnetic separation, and froth flotation. Concentration of ore is a method used to remove unwanted substances from ores and increase the quality of the ore. This process can also involve the use of chemicals, such as leaching agents, which break down substances in the ore, leaving behind valuable metals. Extraction of metal from its oxide is the process of obtaining a pure metal from its oxide. This is typically achieved by reducing the metal oxide to the pure metal using a reducing agent, such as carbon or carbon monoxide. Conversion of ore to oxide is a process in which a metal ore is converted into its oxide. The conversion is usually performed by roasting or calcination, which involves heating the ore in the presence of oxygen.

Dressing of ore is a process that uses mechanical methods to remove unwanted materials from the ore, without altering its chemical composition. Concentration of ore can involve chemical methods such as leaching agents. However, this process aims to increase the quality of the ore, not separate chemicals from each other. Extraction of metal from its oxide uses a chemical process that involves separating the metal from its oxide using a reducing agent. Conversion of ore to oxide involves heating the ore in the presence of oxygen, which can be considered a chemical process. However, the purpose of this process is to convert the ore into its oxide, not to separate chemicals from each other.

Based on the explanations given in the step 2, we can determine that the chemical separation method is most closely associated with option (c) extraction of metal from its oxide. This is because this method separates a metal from its oxide using a chemical reaction and a reducing agent.