Write the name of two important kinds of holes normally encountered in a closed packed structure. How many such holes are present per sphere in a close packed arrangement?

Explanation

To solve the question, we will break it down into two parts: identifying the types of holes in a close-packed structure and determining how many of each type of hole are present per sphere.

### Step-by-Step Solution:

1. **Identify the Types of Holes:**
- In a close-packed structure, the two important types of holes are:
- **Tetrahedral Holes**
- **Octahedral Holes**
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