Amongst the following the number of oxide(s) which are paramagnetic...

The magnetic properties of a substance can be determined by examining its electron configuration: If it has unpaired electrons, then the substance is paramagnetic and if all electrons are paired, the substance is then diamagnetic.

${KO}_{2}$ is potassium superoxide. There is one unpaired electron in anti-bonding molecular orbital of superoxide. Potassium superoxide is paramagnetic due to the presence of unpaired electron.

${NO}_{2}, {ClO}_{2}, NO$ are odd electron species. Hence, they are paramagnetic.

The other are monoxide and dioxide contain paired electrons, so they will show diamagnetic behaviour.