The normal rain water is slightly acidic and its pH value is \( 5.6 \) because of which one of the following?
\( 4\mathrm{NO_2} + \mathrm{O_2} + 2\mathrm{H_2O} \rightarrow 4\mathrm{HNO_3} \)
\( 2\mathrm{SO_2} + \mathrm{O_2} + 2\mathrm{H_2O} \rightarrow 2\mathrm{H_2SO_4} \)
\( \mathrm{N_2O_5} + \mathrm{H_2O} \rightarrow 2\mathrm{HNO_3} \)
\( \mathrm{CO_2} + \mathrm{H_2O} \rightarrow \mathrm{H_2CO_3} \)