A: magnetic field lines are continuous and form closed loops.
R: Magnetic monopoles do not exist.

Options

A. If both Assertion & Reason are the true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reson is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

To solve the question, we need to analyze the Assertion (A) and Reason (R) provided:

**Assertion (A):** Magnetic field lines are continuous and form closed loops.
**Reason (R):** Magnetic monopoles do not exist.

### Step-by-Step Solution:

1. **Understanding Magnetic Field Lines:**
- Magnetic field lines represent the direction and strength of the magnetic field. They are drawn such that they indicate the path a north pole of a magnet would take in the field.

2. **Characteristics of Magnetic Field Lines:**
- Magnetic field lines are continuous, meaning they do not break or have endpoints. They always form closed loops, which implies that they return to their starting point.
- This continuity indicates that there are no isolated magnetic poles (monopoles), as each line must connect a north pole to a south pole.

3. **Implication of Magnetic Monopoles:**
- The absence of magnetic monopoles means that every magnetic field must have both a north and a south pole. If a monopole existed, it would create a situation where magnetic field lines could start or end at that point, contradicting the continuous nature of the field lines.

4. **Conclusion on Assertion and Reason:**
- Since magnetic field lines are indeed continuous and form closed loops, and this behavior is due to the non-existence of magnetic monopoles, both the assertion and reason are correct.
- Furthermore, the reason provided gives a valid explanation for the assertion.

5. **Final Answer:**
- Both the assertion (A) and the reason (R) are correct, and the reason correctly explains the assertion. Therefore, the answer is option 1.