The correct option is C Hydrochloric acid and potassium hydroxide
When definite amounts of acid and base (alkali) are mixed, they neutralise each other forming salt and water. The general representation is given below.
Acid + base → salt + water
Thus, hydrochloric acid and potassium hydroxide neutralise each other forming potassium chloride and water. The reaction can be represented as:
Hydrochloric acid + Potassium hydroxide → Potassium chloride + Water
Sodium hydroxide and potassium hydroxide are bases. Two bases cannot neutralise each other. Similarly, hydrochloric acid and sulphuric acid will not neutralise each other as both are acids. Also, water does not neutralise an acid or a base.