In the extraction of iron, the most preferred ores are (a) hematite and limonite (b) copper pyrites and siderite (c) magnetite and iron pyrites (d) limonite and copper pyrites

The extraction of iron mostly takes place in a blast furnace. The raw materials needed are iron ore, coke (a reducing agent), and limestone (used as a flux). The process starts by heating the furnace with a supply of hot air, which reacts with the coke to produce carbon monoxide. This then reduces the iron ore to pure iron, which sinks to the bottom of the furnace. The limestone serves as a flux by removing impurities, such as silica, and the slag floats on top of the molten iron.

Properties of the ores mentioned in the options: (a) Hematite (Fe2O3) - It is an iron oxide with a high iron content (about 70%) Limonite (Fe2O3•H2O) - It is a hydrated iron oxide with a lower iron content compared to hematite. (b) Copper Pyrites (CuFeS2) - Mainly composed of copper, with a small amount of iron. Siderite (FeCO3) - A carbonate iron ore containing about 48% of iron. (c) Magnetite (Fe3O4) - A magnetic iron oxide with a high iron content (about 72% of iron). Iron Pyrites (FeS2) - Also called fool's gold, has low iron content compared to other iron ores. (d) Limonite - As mentioned earlier, it is a hydrated iron oxide with a lower iron content. Copper Pyrites - As mentioned earlier, it is mainly composed of copper, with a small amount of iron.

Based on the iron content and the properties of the ores, the most preferred ores for iron extraction would be ones with a high iron content and minimal impurities. From the provided options, ores in option (a) – hematite and limonite – meet these criteria, as they have high iron content, and the extraction process is relatively simpler compared to the other ores provided. Therefore, the correct answer is: (a) hematite and limonite.