The cyanide complex of silver formed in the silver extraction in Mac-Arthur's Forrest cyanide process is

Which of the following oxides can be reduced to the metal by heating it in a stream of hydrogen?

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,

Chromium is obtained by reducing concentrated chromite ore with

The metallurgical process in which a metal is obtained in a fused state is called:

Parke's process is used to extract