Ionic Equilibrum

Phosphoric acid ionizes in three steps with their ionization constant values $K_{a_1}, K_{a_2}$ and $K_{a_3}$, respectively, while $K$ is the overall ionization constant. Which of the following statements are true?

A. $\quad \log \mathrm{K}=\log \mathrm{K}_{\mathrm{a}_1}+\log \mathrm{K}_{\mathrm{a}_2}+\log \mathrm{K}_{\mathrm{a}_3}$

B. $\mathrm{H}_3 \mathrm{PO}_4$ is a stronger acid than $\mathrm{H}_2 \mathrm{PO}_4^{-}$and $\mathrm{HPO}_4^{2-}$

C. $K_{a_1}>K_{a_2}>K_{a_3}$

D. $K_{a_1}=\frac{K_{a_3}+K_{a_2}}{2}$

Choose the correct answer from the options given below :