Final answer:
A patient with type B antigens on their erythrocytes and producing anti-A antibodies has type B blood.
Step-by-step explanation:
A patient who has type B antigens on the surface of their erythrocytes and produces anti-A antibodies has type B blood. This is because individuals with blood type B have B antigens present on their red blood cells (RBCs) and naturally produce antibodies against A antigens, referred to as anti-A antibodies. Moreover, it is worth noting that individuals with blood type AB have both A and B antigens on their RBCs and do not produce either anti-A or anti-B antibodies, making them universal recipients. Conversely, individuals with blood type O lack both A and B antigens on their RBCs but produce both anti-A and anti-B antibodies, making them universal donors.