Which of the following describes the hexagonal close packed arrangement of spheres ?

Options

A. ABCABA
B. ABCABC
C. ABABA
D. ABBABB

Answer

To describe the hexagonal close packed (HCP) arrangement of spheres, we can break down the solution into a step-by-step explanation:

### Step-by-Step Solution:

1. **Understanding HCP Structure**:
- The hexagonal close packed (HCP) structure consists of layers of spheres arranged in a specific order.

2. **Layer Arrangement**:
- The arrangement starts with the first layer of spheres, which we will label as Layer A.

3. **Adding the Second Layer**:
- On top of Layer A, we place a second layer, which we will label as Layer B. The spheres in Layer B fit into the gaps of Layer A.

4. **Adding the Third Layer**:
- The third layer is placed on top of Layer B and is labeled as Layer C. The spheres in Layer C also fit into the gaps of Layer B.

5. **Repeating the Pattern**:
- After Layer C, the pattern repeats. The fourth layer is similar to Layer A, and the fifth layer is similar to Layer B, followed by another Layer C. This creates a continuous sequence of layers.

6. **Identifying the Sequence**:
- The overall sequence of layers in HCP can be described as ABC, ABC, ABC, and so on. This indicates that the arrangement of spheres in HCP follows this repeating pattern.

7. **Conclusion**:
- Therefore, the correct description of the hexagonal close packed arrangement of spheres is that it follows the ABC, ABC pattern.

### Final Answer:
The hexagonal close packed arrangement of spheres is described by the sequence ABC, ABC, ABC, and so on.

---