Equilibrium

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

A. $\log K = \log K_{a_1} + \log K_{a_2} + \log K_{a_3}$

B. $\mathrm{H_3PO_4}$ is a stronger acid than $\mathrm{H_2PO_4^-}$ and $\mathrm{HPO_4^{2-}}$

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

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

Choose the correct answer from the options given below: