What is the relationship between ${\text{p}}{K_{\text{a}}}$, ${\text{p}}{K_{\text{b}}}$ and ${\text{p}}{K_{\text{w}}}$ for a conjugate acid–base pair?

A.     ${\text{p}}{K_{\text{a}}} = {\text{p}}{K_{\text{w}}} + {\text{p}}{K_{\text{b}}}$

B.     ${\text{p}}{K_{\text{a}}} = {\text{p}}{K_{\text{w}}} - {\text{p}}{K_{\text{b}}}$

C.     ${\text{p}}{K_{\text{a}}} \times {\text{p}}{K_{\text{b}}} = {\text{p}}{K_{\text{w}}}$

D.     $\frac{{{\text{p}}{K_{\text{a}}}}}{{{\text{p}}{K_{\text{b}}}}} = {\text{p}}{K_{\text{w}}}$

B