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
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R :
Assertion A : In the photoelectric effect, the electrons are ejected from the metal surface as soon as the beam of light of frequency greater than threshold frequency strikes the surface.
Reason R : When the photon of any energy strikes an electron in the atom, transfer of energy from the photon to the electron takes place.
In the light of the above statements, choose the most appropriate answer from the options given below :