The set that represents the pair of neutral oxides of nitrogen is:

A neutral oxide is one that is neither acidic nor basic — it does not react with either acids or bases to form salts.

Among the oxides of nitrogen: $$\text{N}_2\text{O}$$ (nitrous oxide) is a neutral oxide as it does not react with water, acids, or bases under normal conditions. $$\text{NO}$$ (nitric oxide) is also a neutral oxide as it does not form any acid or base when dissolved in water.

On the other hand, $$\text{N}_2\text{O}_3$$ is the anhydride of nitrous acid ($$\text{HNO}_2$$) and is acidic. $$\text{NO}_2$$ is also acidic, as it reacts with water to form a mixture of nitric acid and nitrous acid.

Therefore, the pair of neutral oxides of nitrogen is $$\text{NO}$$ and $$\text{N}_2\text{O}$$.