The ratio of the concentration of a $\_\_\_\_\_\_\_\_$ over $\_\_\_\_\_\_\_\_$ describes the proportions of forms of a weak acid necessary to satisfy the Henderson$-$Hasselbalch equation.

a$)$ weak acid; conjugate base

b$)$ conjugate base; weak acid

c$)$ proton donor; proton acceptor

d$)$ proton acceptor; proton donor

e$)$ Answers B & D

f$)$Answers A & C