**Explanation:**

**Bases and Hydroxide Ions:**
- Bases are substances that can accept or donate a pair of electrons (Lewis base) or donate a hydroxide ion (Arrhenius base) in a chemical reaction.
- When a base dissolves in water, it generates hydroxide ions (OH-) as one of its products.
- The presence of hydroxide ions in an aqueous solution is a characteristic property of bases.

**Hydroxide Ions in Water:**
- When bases dissolve in water, the hydroxide ions (OH-) are formed due to the reaction between the base and water molecules.
- The hydroxide ions are formed by the dissociation of water molecules, where one water molecule acts as an acid (donates a proton - H+) and the other water molecule acts as a base (accepts a proton - H+).
- The reaction can be represented as follows: H2O + H2O ⇌ H3O+ + OH-
- In this reaction, the hydroxide ion (OH-) is formed by the acceptance of a proton (H+) by one water molecule.

**Answer:**
- Based on the above explanation, the correct answer is option 'C' - OH-.
- Bases generate hydroxide ions (OH-) in water as one of their products.
- The hydroxide ions contribute to the basic nature of the solution and are responsible for the characteristic properties of bases.
- The presence of hydroxide ions can be tested using indicators or by measuring the pH of the solution.