Which antibodies are found in the plasma of a person with type A blood?

The correct option is anti B, but not anti A.

To understand why this is correct, let us look at the relationship between antigens and antibodies in the ABO blood group system:
1. Antigens on Red Blood Cells: The blood type is determined by the presence of specific markers called antigens on the surface of red blood cells. A person with type A blood has A antigens on their red blood cells.
2. Antibodies in the Plasma: The blood plasma contains antibodies that recognize and target foreign antigens (antigens that are not naturally present on the person's own red blood cells).

Applying this to a person with type A blood:
- Since they have A antigens on their red blood cells, their immune system recognizes A antigens as "self" and does not produce anti-A antibodies. If it did, the anti-A antibodies would attack their own red blood cells.
- Since they do not have B antigens on their red blood cells, their body recognizes the B antigen as foreign. As a result, they naturally produce anti-B antibodies in their plasma.

Therefore, the plasma of a person with type A blood contains anti-B antibodies, but not anti-A antibodies.