D And F Block Elements

Consider the following reactions

$$ \begin{aligned} & \mathrm{A}+\underset{\substack{ \text { Little } \\ \text { amount }}}{\mathrm{NaCl}}+\mathrm{H}_2 \mathrm{SO}_4 \rightarrow \mathrm{CrO}_2 \mathrm{Cl}_2+\text { Side Products } \\ & \mathrm{CrO}_2 \mathrm{Cl}_{2 \text { (Vapour) }}+\mathrm{NaOH} \rightarrow \mathrm{~B}+\mathrm{NaCl}+\mathrm{H}_2 \mathrm{O} \\ & \mathrm{~B}+\mathrm{H}^{+} \rightarrow \mathrm{C}+\mathrm{H}_2 \mathrm{O} \end{aligned} $$

The number of terminal ' $O$ ' present in the compound ' C ' is__________