The correct statement(s) about O3 is(are):
O−O bond lengths are equal
Thermal decomposition of O3 is endothermic
O3 is diamagnetic in nature
O3 has a bent structure
Ozone has two resonance structures and the central oxygen atom always has a single bond with one oxygen and a double bond with the other terminal oxygen atom. Both contributors are equivalent and in practice, the spectroscopic data reveals that all the bonds are equal in length – much like what we would expect from a resonance hybrid.
Unlike O2,O3 has all electrons paired and hence it is diamagnetic.
As you can see, it features a bent structure. What about the decomposition of Ozone to oxygen?
Also, decomposition of ozone is exothermic.
2O3→2O2+68 kCal
Hence, all the options are correct.