Assertion: An AC can be transmitted over long distances without much power loss.
Reason: An AC can be stepped up or down with the help of a transformer.

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 Assertion is false but Reason is true.

Answer

To analyze the assertion and reason provided in the question, we will break down the concepts involved in the transmission of alternating current (AC) and the role of transformers.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "An AC can be transmitted over long distances without much power loss."
- This is true because AC transmission allows for high voltage transmission, which reduces current and subsequently minimizes resistive losses (I²R losses) in the transmission lines.

2. **Understanding the Reason**:
- The reason states that "An AC can be stepped up or down with the help of a transformer."
- This is also true. Transformers are devices that can increase (step up) or decrease (step down) the voltage of AC. By stepping up the voltage for transmission, the current can be reduced, which further reduces power loss during transmission.

3. **Analyzing the Relationship**:
- While both the assertion and reason are true, the reason does not directly explain the assertion. The assertion is about power loss during transmission, while the reason discusses the functionality of transformers in adjusting voltage levels.

4. **Conclusion**:
- Therefore, the assertion is true, and the reason is true, but the reason is not the correct explanation of the assertion. Thus, the correct answer is that the assertion is true, and the reason is true, but the reason does not explain the assertion.

### Final Answer:
- Assertion: True
- Reason: True
- Explanation: The reason is not the correct explanation of the assertion.