Hemoglobin contains

Options

A. `Fe^(++)`
B. `Mg^(++)`
C. `Na^(++)`
D. `Ca^(++)`

Answer

### Step-by-Step Solution:

1. **Understanding Hemoglobin**:
- Hemoglobin is a red pigment found in red blood cells. It is primarily responsible for transporting oxygen from the lungs to the rest of the body and returning carbon dioxide from the body back to the lungs.

2. **Composition of Hemoglobin**:
- Hemoglobin is composed of four subunits, each containing a heme group. Each heme group contains an iron (Fe) ion at its center.

3. **Role of Iron in Hemoglobin**:
- The iron in the heme group is crucial because it binds to oxygen molecules. This binding is what allows hemoglobin to transport oxygen effectively.

4. **Elimination of Other Options**:
- The question may present other elements (like magnesium, sodium, or calcium) as options. However, these elements are not part of the hemoglobin structure. Only iron is a key component of hemoglobin.

5. **Conclusion**:
- Therefore, the correct answer to the question "Hemoglobin contains" is that it contains iron.