'A' and 'B' in the above reactions are:

The complex that dissolves in water is :

Given below are two statements:

Statement-I : Methane and steam passed over a heated $$\mathrm{Ni}$$ catalyst produces hydrogen gas.

Statement-II : Sodium nitrite reacts with $$\mathrm{NH}_{4} \mathrm{Cl}$$ to give $$\mathrm{H}_{2} \mathrm{O}, \mathrm{N}_{2}$$ and $$\mathrm{NaCl}$$.

In the light of the above statements, choose the most appropriate answer from the options given below :

In the extraction process of copper, the product obtained after carrying out the reactions

(i) $$2 \mathrm{Cu}_{2} \mathrm{~S}+3 \mathrm{O}_{2} \rightarrow 2 \mathrm{Cu}_{2} \mathrm{O}+2 \mathrm{SO}_{2}$$

(ii) $$2 \mathrm{Cu}_{2} \mathrm{O}+\mathrm{Cu}_{2} \mathrm{~S} \rightarrow 6 \mathrm{Cu}+\mathrm{SO}_{2}$$ is called