Assertion : Ozone is a powerful oxidising agent in comparison to ${\text{O}}_2$.Reason : Ozone is diamagnetic but ${\text{O}}_2$ is paramagnetic.

Ozone (${\text{O}}_3$) is a powerful oxidizing agent because it easily liberates nascent oxygen: ${\text{O}}_3\to {\text{O}}_2+\text{O}$. It is true that ${\text{O}}_3$ is diamagnetic and ${\text{O}}_2$ is paramagnetic (due to two unpaired electrons), but this magnetic property difference is not the reason for the difference in oxidizing power.