Assertion (A) : Covalent crystals have higher melting point.
Reason (R ) : Covalent bonds are stronger than ionic bonds.

Options

A. If both `(A)` and `(R)` are correct, and `(R)` is the correct explanation of `(A)`
B. If both `(A)` and `(R)` are correct, but `(R)` is not the correct explanation of `(A)`
C. If `(A)` is correct, but `(R)` is incorrect.
D. If both `(A)` is incorrect but `(R)` is correct.

Explanation

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

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that "Covalent crystals have higher melting point."
- Generally, covalent crystals (like diamond) do have high melting points, but they are not necessarily higher than those of ionic crystals (like sodium chloride). In fact, ionic crystals typically have higher melting points due to the strong electrostatic forces between the oppositely charged ions.

2. **Understanding the Reason (R)**:
- The reason states that "Covalent bonds are stronger than ionic bonds."
- This statement is incorrect. Ionic bonds, which result from the complete transfer of electrons and the resulting electrostatic attraction between ions, are generally stronger than covalent bonds, which involve the sharing of electrons.

3. **Evaluating the Truth of A and R**:
- Since the assertion (A) is incorrect (covalent crystals do not have higher melting points than ionic crystals), we can conclude that A is false.
- The reason (R) is also incorrect because covalent bonds are not stronger than ionic bonds.

4. **Conclusion**:
- Both the assertion (A) and the reason (R) are incorrect.

### Final Answer:
Both A and R are incorrect.

### Options:
- The correct option is **D**: Both A and R are incorrect.