What blood types are most desired for plasma donation?

All ok. If only the plasma is being transfused from a donor to a recipient, and absolutely no red blood cells, then blood type is not significant. Blood types only refer to the red blood cells; the bone marrow also produces platelets and white blood cells. The serum or plasma is the clear yellow fluid part of the blood.
All are good. All plasma types are needed for transfusion in different situations. The universal plasma is ab because it does not have anti-a or anti-b and can be transfused to all blood types a, b, ab and o. It is important to know the ABO type of the patient to transfuse the right plasma and avoid hemolysis in patient's blood. Knowing rh type is not necessary for plasma transfusion unless it contains red cells.