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 given information, we can follow these steps:

### Step 1: Understand the characteristics of antibodies
Antibodies, also known as immunoglobulins, are glycoproteins produced by B cells in response to antigens. There are different classes of antibodies, each with unique properties.

### Step 2: Analyze the given information
The question provides two key pieces of information:
1. The antibody exists as a monomer.
2. It has the highest concentration in the blood.

### Step 3: List the types of antibodies
The main classes of antibodies are:
- IgG
- IgM
- IgA
- IgE

### Step 4: Evaluate each antibody type based on the criteria
1. **IgG**:
- Exists as a monomer.
- Constitutes about 80% of the total serum immunoglobulin, making it the most abundant antibody in the blood.

2. **IgM**:
- Exists as a pentamer (not a monomer).
- Constitutes about 5-10% of total immunoglobulin.

3. **IgA**:
- Generally exists as a dimer.
- Constitutes about 10-15% of total immunoglobulin.

4. **IgE**:
- Exists as a monomer.
- Constitutes a very small percentage (1-2%) of total immunoglobulin.

### Step 5: Conclusion
Based on the analysis, the only antibody that meets both criteria (exists as a monomer and has the highest concentration in the blood) is **IgG**.

### Final Answer
The antibody is **IgG**.

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