Ionisation constant of a weak acid (HA) in terms of `A_(m)^(oo)` and `A_(m)` is:
A. `K_(a)=(CA_(m)^(oo))/((A_(m)-A^(oo)))`
B. `k_(a)=(CA_(m)^(2))/(A_(m)^(oo)(A_(m)^(00)-A_(m)))`
C. `K_(a)=(C(A_(m)^(oo))^(2))/(A_(m)^(oo)(A_(m)^(oo)-A_(m)))`
D. None of these
