Assertion: S.I. unit of atomic mass and molecular mass is kilograms.
Reason : Atomic mass is equal to the mass of `6.023xx 10^(24)` atoms.

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 assertion is true but reason is false
D. If both assertion and reason are false.

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 the SI unit of atomic mass and molecular mass is kilograms.
- However, the standard unit used for atomic mass is the atomic mass unit (AMU), not kilograms. While it is true that 1 AMU can be converted to kilograms (1 AMU = 1.66 x 10^-27 kg), atomic mass is typically expressed in AMU.

2. **Understanding the Reason**:
- The reason states that atomic mass is equal to the mass of `6.023 x 10^24` atoms.
- This is incorrect because the atomic mass is defined based on the mass of `6.022 x 10^23` atoms (Avogadro's number). Therefore, the statement should refer to `6.022 x 10^23` atoms, not `6.023 x 10^24`.

3. **Evaluating the Assertion and Reason**:
- Since the assertion is incorrect (the SI unit of atomic mass is not kilograms) and the reason is also incorrect (the mass is not based on `6.023 x 10^24` atoms), both statements are false.

4. **Conclusion**:
- Therefore, the correct answer is that both the assertion and the reason are false.

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