H-bond between-`NH_2` group of one amino acid with the -CO group of ........ ...... amino acid takes place in the formation of a-helix.

Explanation

To answer the question regarding the hydrogen bond formation in the alpha helix structure of proteins, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding the Structure of Alpha Helix**:
- The alpha helix is a common secondary structure found in proteins. It is characterized by a right-handed coil or spiral.

2. **Identifying the Components Involved**:
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