ethanoic acid

The answer is B.

In water, CH3COOH(aq) is partly ionized to give CH3COO-(aq) and H+(aq) ions.
CH3COOH(aq) = CH3COO-(aq) + H+(aq)
Since the reaction is reversible, CH3COOH is not completely reacted. Therefore, the solution contains a certain amount of CH3COOH(aq), CH3COO-(aq) and H+(aq).

Water is self-ionized to the give H+(aq) and OH-(aq)
In any solution, the higher the concentration of H+(aq) ions, the lower the concentration of OH-(aq) ions.
Since the solution is acidic and H+(aq) is not low, there is only a very small amount of OH-(aq) ions.

B. OH-

.CH3COOH(aq) = CH3COO-(aq) + H+(aq)
reversible reaction. CH3COOH is a weak acid.