AB blood group does not have any antibodies in plasma. That's why AB blood group is universal recipient.

Blood groups are determined by the presence or absence of certain antigens on the surface of red blood cells. There are four main blood types: A, B, AB, and O. In addition to the antigens, individuals also have antibodies in their blood plasma that are specific to the antigens they do not possess.

Manoj has AB blood group, which means that his red blood cells possess both A and B antigens. Since he has both antigens, he does not produce antibodies against them. This is why the correct answer is option 'D' - no antibodies are present in his blood plasma.

To further understand this concept, let's break down the different blood groups and the corresponding antibodies:

1. Blood Group A:
- Antigen on red blood cells: A
- Antibody in blood plasma: anti-B

2. Blood Group B:
- Antigen on red blood cells: B
- Antibody in blood plasma: anti-A

3. Blood Group AB:
- Antigens on red blood cells: A and B
- No antibodies in blood plasma against A or B antigens

4. Blood Group O:
- No antigens on red blood cells
- Antibodies in blood plasma: both anti-A and anti-B

The presence of antibodies in the blood plasma is a natural defense mechanism of the immune system. If a person receives a blood transfusion with incompatible blood, the antibodies in their plasma can recognize and attack the antigens on the transfused red blood cells, leading to a potentially severe immune reaction.

In the case of Manoj, since he has AB blood group, he can receive blood transfusions from any blood type (A, B, AB, or O) without any major immune reactions. This is because his blood cells possess both antigens (A and B), and therefore, his plasma does not contain antibodies against these antigens.

In summary, individuals with AB blood group do not have antibodies against A or B antigens in their blood plasma. This makes them universal recipients for blood transfusions, as they can receive blood from any blood type without significant immune reactions.