A: An azeotropic solution of two liquids has boiling point lower than either of them.
R: Solution shows +ve deviation from ideal behaviour.

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided in the statement.

### Assertion (A):
**An azeotropic solution of two liquids has a boiling point lower than either of them.**

1. **Definition of Azeotropic Solution**: An azeotropic solution is a mixture of two or more liquids that has a constant boiling point and composition throughout the distillation process. This means that when the mixture is boiled, it vaporizes in the same proportion as it exists in the liquid phase.

2. **Boiling Point Comparison**: In the case of certain azeotropic mixtures, the boiling point of the mixture can indeed be lower than the boiling points of the individual components. This is particularly true for mixtures that exhibit positive deviation from Raoult's law.

3. **Conclusion on Assertion**: Therefore, the assertion is correct.

### Reason (R):
**Solution shows +ve deviation from ideal behavior.**

1. **Understanding Positive Deviation**: Positive deviation from Raoult's law occurs when the vapor pressure of the solution is greater than what would be predicted based on the individual components' vapor pressures. This happens due to weaker intermolecular forces in the mixture compared to the pure components.

2. **Effect on Boiling Point**: Because the vapor pressure is higher than expected, the boiling point of the azeotropic mixture is lower than that of the individual components. This is a direct consequence of the positive deviation.

3. **Conclusion on Reason**: Thus, the reason provided is also correct.

### Final Conclusion:
Both the assertion and the reason are correct, and the reason correctly explains the assertion.

### Summary:
- Assertion (A) is correct: An azeotropic solution can have a boiling point lower than either component.
- Reason (R) is correct: The solution shows positive deviation from ideal behavior, leading to a higher vapor pressure and a lower boiling point.