Assertion: Melting points of isomeric dihalobenzenes are nearly the same.
Reason: Isomeric dihalobenzenes have different molecular masses.

Options

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

Explanation

To analyze the given assertion and reason regarding isomeric dihalobenzenes, we can break down the problem step by step.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "melting points of isomeric dihalobenzenes are nearly the same."
- Isomeric dihalobenzenes refer to compounds that have the same molecular formula but different structural arrangements (isomers). For dihalobenzenes, the isomers can be ortho, meta, and para.

2. **Analyzing the Melting Points**:
- Generally, isomers can have different physical properties, including melting points.
- In the case of dihalobenzenes, the melting points can vary significantly due to the different spatial arrangements of the halogen atoms, which affects how well the molecules pack in a solid state.
- For example, para-dihalobenzene typically has a higher melting point than ortho- and meta-isomers due to its symmetrical structure allowing for better packing.

3. **Understanding the Reason**:
- The reason states that "isomeric dihalobenzenes have different molecular masses."
- This statement is incorrect. Isomers, by definition, have the same molecular formula and therefore the same molecular mass. The only difference between them is their structural arrangement.

4. **Conclusion**:
- Since the assertion is incorrect (melting points are not nearly the same) and the reason is also incorrect (isomeric dihalobenzenes do not have different molecular masses), we conclude that both the assertion and reason are false.

### Final Answer:
Both the assertion and the reason are false.