The neutral oxide among the following is

According to the question, Neutral oxides are those oxides which show neither basic nor acidic properties when they react with water. Some examples of neutral oxides are  nitrous oxide $\left({\mathrm{N}}_2\mathrm{O}\right)$, nitric oxide  $\left(\mathrm{NO}\right)$, carbon monoxide (CO). Which are only slightly soluble in water.

Whereas ${\mathrm{SO}}_2$ & ${\mathrm{CO}}_2$ Is acidic oxide, because when they dissolve in water they form sulphurs acid and carbonic acid.

CaO (metal oxide) is basic in nature and when it reacts with water then it forms $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$.