In which of the following cases is the approximation that the equilibrium concentration of H+ (aq) is

Question:

In which of the following cases is the approximation that the equilibrium concentration of H+ (aq) is small relative to the initial concentration of HA likely to be most valid:
(a) Initial [HA] = 0.100 M and Ka = 1.0 ( 10-6,
(b) Initial [HA] = 0.100 M and Ka = 1.0 ( 10-4,
(c) Initial [HA] = 1.00 M and Ka = 1.0 ( 10-6?