Assertion: After white washing the walls, a shiny white finish on walls is obtained after two to three days.
Reason: Calcium Oxide reacts with Carbon dioxide to form Calcium Hydrogen Carbonate which gives shiny white finish.

Options

A. Both A and R are true, and R is correct explanation of the assertion.
B. Both A and R are true, but R is not the correct explanation of the assertion.
C. A is true, but R is false.
D. A is false, but R is true.

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that after whitewashing the walls, a shiny white finish is obtained after two to three days.
- This is true because when whitewashing is done, the calcium oxide (CaO) in the whitewash reacts with carbon dioxide (CO2) in the air over time, leading to the formation of calcium carbonate (CaCO3), which is known for its shiny appearance.

2. **Understanding the Reason**:
- The reason given is that calcium oxide reacts with carbon dioxide to form calcium hydrogen carbonate, which gives a shiny white finish.
- This part is partially correct in that calcium oxide does react with carbon dioxide, but the product formed is calcium carbonate (CaCO3), not calcium hydrogen carbonate. Therefore, this statement is false.

3. **Conclusion**:
- Since the assertion is true (shiny finish is obtained) and the reason is false (incorrect product formation), we conclude that the assertion is true and the reason is false.

### Final Answer:
- The correct answer is that the assertion is true and the reason is false.