Mark out the correct options.

Options

A. (a)Diamagnetism occurs in all materials
B. (b)Diamagnetism results from the partial alignment of permanent magnetic moment.
C. (c)The magnetizing field intensity `H` is always zero in free space.
D. (d)The magnetic field of induced magnetic moment is opposite to the applied fied.

Answer

To solve the question, we need to analyze each of the given options regarding their correctness based on the principles of magnetism, particularly focusing on diamagnetism.

### Step-by-Step Solution:

1. **Evaluate Option A: "Diamagnetism occurs in all materials."**
- Diamagnetism is a property that is present in all materials, although it may be overshadowed by other magnetic properties like ferromagnetism or paramagnetism in certain materials. Therefore, this statement is **true**.

2. **Evaluate Option B: "Diamagnetism results from a partial alignment of permanent magnetic moment."**
- Diamagnetism does not involve the alignment of permanent magnetic moments. Instead, it arises from the induced magnetic moments in the presence of an external magnetic field, which oppose the applied field. Thus, this statement is **false**.

3. **Evaluate Option C: "The magnetizing field intensity H is always 0 in free space."**
- The magnetizing field intensity \( H \) can be zero in free space, but it is not always zero. In many cases, it can be defined and is not necessarily zero. Therefore, this statement is **false**.

4. **Evaluate Option D: "The magnetic field of induced magnetic moment is opposite to the applied field."**
- This statement is true. In diamagnetic materials, the induced magnetic moment is indeed opposite to the direction of the applied magnetic field, which is a characteristic of diamagnetism. Thus, this statement is **true**.

### Final Conclusion:
- The correct options are **A** and **D**.