${\mathrm{ClO}}_2$ is paramagnetic and contains odd number electrons but does not dimerize, because:

Odd valence electrons make up the molecule ${\mathrm{ClO}}_2$. It is therefore of a paramagnetic character. In order to couple the electrons, this strange electron molecule now has to dimerize, but ${\mathrm{ClO}}_2$ does not.

So, ${\mathrm{ClO}}_2$ is paramagnetic and contains odd number electrons but does not dimerize, because odd electron of ${\mathrm{ClO}}_2$ occupies ${\mathrm{sp}}^3$ hybrid orbital.

Hence, the option D is correct.