D And F Block Elements

Correct statements from the following are

A. Potassium dichromate is an oxidising agent and it oxidises $\mathrm{FeSO}_4$ to $\mathrm{Fe}_2\left(\mathrm{SO}_4\right)_3$ in acidic medium.

B. Sodium dichromate can be used as primary standard in volumetric estimation.

C. $\mathrm{CrO}_4^{2-}$ and $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$ are interconvertible in aqueous solution by varying the pH of the solution.

D. $\mathrm{Cr}-\mathrm{O}-\mathrm{Cr}$ bond angle in $\mathrm{Cr}_2 \mathrm{O}_7^{2-}$ is $126^{\circ}$.

Choose the correct answer from the options given below :