If a blood type ends in + (positive) that means

The correct option is: you are positive for an Rh protein.

Blood types are determined by the presence or absence of specific antigens (proteins) on the surface of red blood cells. The ABO blood group system classifies blood into types A, B, AB, or O based on A and B antigens.

In addition to the ABO system, the Rh (Rhesus) factor is another critical antigen system. If your red blood cells have the Rh antigen (specifically the D antigen) on their surface, your blood type is classified as Rh positive (+). If this antigen is absent, your blood type is classified as Rh negative (-). Therefore, when a blood type ends in a plus sign (for example, O+ or A+), it indicates that you are positive for the Rh protein.