Which of the following exhibit perfect diamagnetism?

Options

A. Conductor
B. Semiconductor
C. Insulator
D. Superconductor

Answer

To determine which of the following materials exhibit perfect diamagnetism, we need to analyze the properties of different materials, particularly focusing on superconductors.

### Step-by-Step Solution:

1. **Understanding Diamagnetism**:
- Diamagnetism is a property of materials that causes them to create an opposing magnetic field when exposed to an external magnetic field. This results in a repulsion from the magnetic field.

2. **Identifying Perfect Diamagnetism**:
- Perfect diamagnetism is a characteristic of materials that completely expel magnetic fields. This phenomenon is observed in superconductors.

3. **Superconductors**:
- Superconductors are materials that exhibit zero electrical resistance and expel magnetic fields when cooled below a certain critical temperature. This behavior is known as the Meissner effect.

4. **Meissner Effect**:
- The Meissner effect is the defining characteristic of superconductors, where they will repel all magnetic field lines from their interior when in the superconducting state, thus demonstrating perfect diamagnetism.

5. **Conclusion**:
- Based on the properties of materials, the only materials that exhibit perfect diamagnetism are superconductors. Therefore, the answer to the question is that superconductors exhibit perfect diamagnetism.

### Final Answer:
- **Superconductors exhibit perfect diamagnetism.**