Identify the antibody on the basis of following information -
I. Exist as monomer II. Highest in concentration in blood .

Options

A. lgG
B. IgM
C. IgE
D. IgA

Answer

To identify the antibody based on the provided information, we can follow these steps:

### Step 1: Analyze the Given Information
The question states two key characteristics of the antibody:
1. It exists as a monomer.
2. It is the highest in concentration in blood.

### Step 2: Review Antibody Types
We need to consider the different types of antibodies (immunoglobulins) and their characteristics:
- **IgG**:
- Exists as a monomer.
- Highest concentration in blood.
- **IgM**:
- Exists as a pentamer (not a monomer).
- First antibody produced in response to an infection.
- **IgA**:
- Usually found as a dimer in secretions, but can exist as a monomer in serum.
- Primarily found in mucosal areas and secretions.
- **IgE**:
- Exists as a monomer.
- Involved in allergic reactions and defense against parasites, but not the highest in blood concentration.

### Step 3: Identify the Correct Antibody
Based on the analysis:
- IgG is the only antibody that meets both criteria: it exists as a monomer and is the highest in concentration in the blood.

### Conclusion
The antibody that fits the description is **IgG**.

### Final Answer
The correct answer is **IgG**.

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