Which of the following element is essential for the formation of protein?

Options

A. `N_2`
B. Na
C. Ca
D. Fe

Explanation

To determine which element is essential for the formation of proteins, we need to analyze the components that make up proteins.

### Step-by-Step Solution:

1. **Understand What Proteins Are**:
- Proteins are large biomolecules that play many critical roles in the body. They are made up of smaller units called amino acids.

**Hint**: Remember that proteins are polymers made from monomers called amino acids.

2. **Identify the Components of Amino Acids**:
- Each amino acid is composed of four key elements: Carbon (C), Hydrogen (H), Oxygen (O), and Nitrogen (N).

**Hint**: Think about the basic structure of amino acids and what elements are involved.

3. **Evaluate the Options Given**:
- The options provided are Nitrogen, Sodium, Calcium, and Iron.
- Among these, we need to identify which one is essential for the formation of proteins.

**Hint**: Recall that proteins are formed from amino acids, which contain specific elements.

4. **Determine the Correct Element**:
- Since amino acids contain Nitrogen, and proteins are made from amino acids, Nitrogen is essential for the formation of proteins.
- Sodium, Calcium, and Iron are not directly involved in the formation of proteins.

**Hint**: Focus on the elements that are part of the amino acid structure.

5. **Conclusion**:
- The correct answer is **Nitrogen**.

### Final Answer:
**Nitrogen is the essential element for the formation of proteins.**