The magnet field lines due to a bar magnet are correctly shown in

Options

A.
B.
C.
D.

Explanation

To solve the question regarding the correct representation of magnetic field lines due to a bar magnet, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of a Bar Magnet**:
- A bar magnet has two poles: a North pole and a South pole. The North pole is typically marked as 'N' and the South pole as 'S'.

2. **Direction of Magnetic Field Lines**:
- Magnetic field lines are defined to originate from the North pole and terminate at the South pole. This means that outside the magnet, the field lines travel from the North pole to the South pole.

3. **Field Lines Inside the Magnet**:
- Inside the bar magnet, the direction of the magnetic field lines is opposite to that outside. They travel from the South pole back to the North pole.

4. **Analyze the Given Options**:
- Look at each option provided in the question. You need to determine which option correctly represents the magnetic field lines based on the rules established above.

5. **Identify the Correct Option**:
- After analyzing the options, you will find that only one option correctly shows the magnetic field lines going from the North pole to the South pole outside the magnet and from the South pole to the North pole inside the magnet.

6. **Conclusion**:
- Based on the analysis, the correct answer is the option that accurately depicts the magnetic field lines as described.

### Final Answer:
- The correct option is **Option 4**.

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