Final answer:
If an unknown blood type reacts with anti-A, anti-B, and anti-Rh antiserums ONLY, it is AB-positive.
Step-by-step explanation:
If an unknown blood type reacts with anti-A, anti-B, and anti-Rh antiserums ONLY, it indicates that the blood type is AB-positive.
In the ABO blood typing system, there are four blood types: A, B, AB, and O. The presence of agglutination (clumping) in the wells with anti-A and anti-B antibodies means that the blood type has both A and B antigens. Additionally, if there is agglutination in the well with anti-Rh antibody, it indicates that the blood type is Rh positive.
Therefore, if an unknown blood type reacts with only these three specific antiserums, it can be identified as AB-positive.