Ferromagnetism arises because of the spontaneous alignment of the magnetic moments due to unpaired electrons as

Options

A. `uparrowuparrowuparrowuparrowuparrow`
B. `uparrowuparrowuparrowdownarrowdownarrow`
C. `uparrowdownarrowuparrowdownarrow`
D. `uparrowuparrowdownarrowuparrowuparrow`

Answer

To solve the question regarding ferromagnetism and the alignment of magnetic moments due to unpaired electrons, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Ferromagnetism**:
- Ferromagnetism is a phenomenon where certain materials exhibit strong magnetic properties. These materials retain their magnetism even when an external magnetic field is removed.

**Hint**: Remember that ferromagnetic materials like iron, nickel, and cobalt can be magnetized and retain their magnetism.

2. **Identify Characteristics of Ferromagnetic Materials**:
- Ferromagnetic substances have unpaired electrons that contribute to their magnetic moments. The key characteristic is the spontaneous alignment of these magnetic moments in a parallel fashion within a domain.

**Hint**: Focus on the role of unpaired electrons in creating magnetic moments.

3. **Analyze the Alignment of Magnetic Moments**:
- In ferromagnetic materials, the magnetic moments align parallel to each other within a domain. This alignment leads to a net magnetic moment.

**Hint**: Visualize how magnetic moments would look in a domain; they should all point in the same direction.

4. **Evaluate the Options**:
- Option A: All spins are parallel → This indicates ferromagnetism.
- Option B: Some spins are parallel, some are anti-parallel → This does not indicate ferromagnetism (could be paramagnetic or anti-ferromagnetic).
- Option C: All spins are anti-parallel → This does not indicate ferromagnetism.
- Option D: Mixed alignment of spins → This does not indicate ferromagnetism.

**Hint**: Compare each option to the characteristics of ferromagnetism; look for parallel alignment.

5. **Select the Correct Answer**:
- Based on the analysis, Option A is the only one that shows the parallel alignment of magnetic moments, which is characteristic of ferromagnetism.

**Hint**: Confirm that the option you choose aligns with the definition and characteristics of ferromagnetism.

### Final Answer:
- The correct alignment of magnetic moments that indicates ferromagnetism is **Option A**.