The purest form of commercial iron is

In the cyanide process involving extraction of silver,zinc is used industrially as an

Silica is added to roasted copper ores during extraction in order to remove

The Ellingham diagram of a certain metal $M$ is represented in the figure. The points $A$ and $B$ respectively correspond to:

Consider the following metallurgical processes:
$(i)$ Heating impure metal with $CO$ and distilling the resulting volatile carbonyl (boiling point $43\,^{\circ}C$) and finally decomposing at $150\,^{\circ}C$ to $200\,^{\circ}C$ to get the pure metal.
$(ii)$ Heating the sulphide ore in air until a part is converted to oxide and then further heating in the absence of air to let the oxide react with unchanged sulphide.
$(iii)$ Electrolysing the molten electrolyte containing approximately equal amounts of the metal chloride and $CaCl_2$ to obtain the metal.
The processes used for obtaining sodium,nickel and copper are,respectively,

In the Hall-Heroult process,which of the following is used for reducing $Al_2O_3$?