The normal rain water is slightly acidic and its $\mathrm{pH}$ value is $5.6$ because of which one of the following?

The element playing significant role in neuromuscular function and interneuronal transmission is :

Cyclohexylamine when treated with nitrous acid yields $(\mathrm{P})$. On treating $(\mathrm{P})$ with $\mathrm{PCC}$ results in (Q). When $(\mathrm{Q})$ is heated with dil. $\mathrm{NaOH}$ we get $(\mathrm{R})$ The final product (R) is :

Given below are two statements :

Statement I : $ \mathrm{H}_{2} \mathrm{O}_{2}$ is used in the synthesis of Cephalosporin

Statement II : $ \mathrm{H}_{2} \mathrm{O}_{2}$ is used for the restoration of aerobic conditions to sewage wastes.

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