Identify the type of reaction taking place when water is added slowly to a small amount of calcium oxide in a beaker is:
(I) Exothermic reaction.
(II) Endothermic reaction
(III) Combination Reaction
(IV)Displacement reaction

Options

A. Both (I) and (III)
B. Both (II) and (III)
C. Both (I) and (IV)
D. Both (II) and (IV)

Explanation

To solve the question of identifying the type of reaction that occurs when water is added slowly to a small amount of calcium oxide (CaO), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants in this scenario are calcium oxide (CaO) and water (H₂O).

2. **Write the Reaction**:
- When water is added to calcium oxide, a chemical reaction occurs, forming calcium hydroxide (Ca(OH)₂):
\[ \text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2 \]

3. **Determine the Type of Reaction**:
- This reaction involves the combination of two substances (CaO and H₂O) to form a single product (Ca(OH)₂). Hence, it is classified as a **combination reaction**.

4. **Check for Heat Release**:
- The reaction is also exothermic, meaning it releases heat. This can be observed as the temperature of the mixture increases when water is added to calcium oxide.

5. **Evaluate the Options**:
- (I) Exothermic reaction: **True** (heat is released)
- (II) Endothermic reaction: **False** (heat is not absorbed)
- (III) Combination Reaction: **True** (two reactants combine to form one product)
- (IV) Displacement reaction: **False** (no element is displaced)

6. **Conclusion**:
- The correct answers are (I) Exothermic reaction and (III) Combination Reaction.

### Final Answer:
The type of reaction taking place when water is added slowly to a small amount of calcium oxide is:
- (I) Exothermic reaction
- (III) Combination Reaction