Mg is present in :

Options

A. Chlorophyll
B. Haemoglobin
C. Vitamin-12
D. Vitamin-B

Answer

To determine where magnesium (Mg) is present among the given options, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- A) Chlorophyll
- B) Hemoglobin
- C) Vitamin B12
- D) Vitamin B

2. **Analyze Option A: Chlorophyll**:
- Chlorophyll is the green pigment found in plants, which is essential for photosynthesis.
- It contains a magnesium ion (Mg²⁺) at its center, which is crucial for its function.
- **Conclusion**: Magnesium is present in chlorophyll.

3. **Analyze Option B: Hemoglobin**:
- Hemoglobin is a protein in red blood cells responsible for transporting oxygen.
- It contains iron (Fe) in its heme group, not magnesium.
- **Conclusion**: Magnesium is not present in hemoglobin.

4. **Analyze Option C: Vitamin B12**:
- Vitamin B12, also known as cobalamin, contains cobalt (Co) as its central metal ion.
- **Conclusion**: Magnesium is not present in vitamin B12.

5. **Analyze Option D: Vitamin B**:
- Vitamin B refers to a group of vitamins, and specifically, vitamin B12 (cobalamin) is included in this group.
- Like vitamin B12, it also contains cobalt.
- **Conclusion**: Magnesium is not present in vitamin B.

6. **Final Conclusion**:
- Among the options provided, magnesium is only present in chlorophyll (Option A).

### Answer:
The correct answer is **A) Chlorophyll**.