Gaseous phase decomposition of $N_2O$ is given below :

Question

Step 1:$N_2O(s)\rightarrow N_2(g)+O(g)$

Step 2:$O(g)+N_2O(g)\rightarrow N_2(g)+O_2(g)$

then reaction intermediate is

$\begin{array}{1 1}(a)\;N_2O(g)&(b)\;N_2(g)\\(c)\;2N_2O(g)&(d)\;O(g)\end{array}$