The reaction of HClO$$_3$$ with HCl gives a paramagnetic gas, which upon reaction with O$$_3$$ produces

The key is to identify the paramagnetic gas formed when $$HClO_3$$ reacts with $$HCl$$ and to know how that gas behaves toward $$O_3$$.

Step 1 : Product of $$HClO_3 + HCl$$
Chloric acid reacts with concentrated hydrochloric acid in the following redox (disproportionation) reaction:
$$2\,HClO_3 + HCl \;\longrightarrow\; 2\,ClO_2 \;+\; Cl_2 \;+\; 2\,H_2O$$

$$ClO_2$$ has an odd number of electrons (it contains one unpaired electron), so it is paramagnetic. Hence the “paramagnetic gas” mentioned is $$ClO_2$$.

Step 2 : Reaction of $$ClO_2$$ with $$O_3$$
When chlorine dioxide is treated with ozone, it dimerises to give dichlorine hexoxide:
$$2\,ClO_2 + O_3 \;\longrightarrow\; Cl_2O_6 + O_2$$

The product formed is $$Cl_2O_6$$.

Among the given options, $$Cl_2O_6$$ corresponds to Option C.

Therefore, the correct answer is:
Option C which is: Cl$$_2$$O$$_6$$