Which of the following reactions is a decomposition redox reaction? 

$2\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2\left(\mathrm{s}\right)\stackrel{\mathrm{\Delta }}{\to }2\mathrm{PbO}\left(\mathrm{s}\right)+4{\mathrm{NO}}_2\left(\mathrm{g}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)$
In redox reaction, oxidation number changes.
(1) Oxidation state of N is decreasing from +5 to +4 .
Oxidation state of N is increasing from -2 to zero.
(2) It is redox synthesis reaction.
N:0 to +2
O: 0 to -2
(3), (4) Disproportionation reaction