Which of the following cannot be used for the preparation of $H_2$?

What do you understand by $(i)$ electron-deficient,$(ii)$ electron-precise,and $(iii)$ electron-rich compounds of hydrogen? Provide justification with suitable examples.

In which of the following reactions is dihydrogen not evolved?

Number of nucleons in $D_2$ molecule is

Given below are two statements :
Statement-$I$: Methane and steam passed over a heated $Ni$ catalyst produces hydrogen gas.
Statement-$II$: Sodium nitrite reacts with $NH_4Cl$ to give $H_2O$,$N_2$ and $NaCl$.
In the light of the above statements,choose the most appropriate answer from the options given below :

Which of the following processes produces hydrogen with the highest purity $(99.9\%)$?