The correct order of acidic character for the oxides of nitrogen is:

Solution

1. Acidic character of non-metal oxides increases with the oxidation state of the central element.
2. The oxidation states are: ${\text{N}}_2\text{O}(+1)$, $\text{NO}(+2)$, ${\text{N}}_2{\text{O}}_3(+3)$, ${\text{NO}}_2(+4)$, ${\text{N}}_2{\text{O}}_5(+5)$.
3. Higher oxidation state leads to higher acidity.
4. The order is ${\text{N}}_2\text{O}<\text{NO}<{\text{N}}_2{\text{O}}_3<{\text{NO}}_2<{\text{N}}_2{\text{O}}_5$.
5. Hence the answer is (A).