Assertion :- Molecular mass of polymers cannot be calculated using boiling point or freezing point method.
Reason : Polymers solutions do not possess a constant boiling point or freezing point.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Explanation

To solve the assertion-reason question regarding the molecular mass of polymers and their boiling/freezing points, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "Molecular mass of polymers cannot be calculated using boiling point or freezing point method."
- This is true because the methods of boiling point elevation and freezing point depression are based on the assumption that the solute behaves ideally, which is not the case for polymers.

2. **Understanding the Reason**:
- The reason states that "Polymers solutions do not possess a constant boiling point or freezing point."
- This statement is misleading. While it is true that polymer solutions can exhibit a range of boiling and freezing points due to their complex nature, it does not mean that they do not have a defined boiling or freezing point. Instead, the behavior of polymers in solution leads to non-ideal solutions, making it difficult to apply these methods accurately.

3. **Evaluating the Assertion and Reason**:
- The assertion is correct: Molecular mass of polymers cannot be accurately determined using boiling point or freezing point methods.
- The reason is incorrect: While polymer solutions may not behave ideally, they can still have defined boiling and freezing points, but the methods are not suitable for determining molecular mass due to the non-ideal behavior.

4. **Conclusion**:
- Since the assertion is true and the reason is false, the correct answer to the question is that the assertion is correct, but the reason is incorrect.

### Final Answer:
- The correct option is: Assertion is true, but reason is false.