The normal rain water is slightly acidic and its pH value is 5.6 because of which one of the following?

\({\mathrm{CO}}_{2}+{\mathrm{H}}_{2}\mathrm{O}\to {\mathrm{H}}_{2}{\mathrm{CO}}_{3}\)

\(4{\mathrm{NO}}_{2}+{\mathrm{O}}_{2}+2{\mathrm{H}}_{2}\mathrm{O}\to 4{\mathrm{HNO}}_{3}\)

\(2{\mathrm{SO}}_{2}+{\mathrm{O}}_{2}+2{\mathrm{H}}_{2}\mathrm{O}\to 2{\mathrm{H}}_{2}{\mathrm{SO}}_{4}\)

\({\mathrm{N}}_{2}{\mathrm{O}}_{5}+{\mathrm{H}}_{2}\mathrm{O}\to 2{\mathrm{HNO}}_{3}\)