HOSA Forensic Science Assessment Practice Test

The presence of the Rh antigen is directly relevant to blood type categorization. The Rh factor, which can be either positive or negative, is a specific protein found on the surface of red blood cells. When determining an individual’s blood type, both the ABO blood group (A, B, AB, and O) and the Rh factor are considered together. For example, a person with type A blood and the Rh factor present is classified as A positive (A+), while the same blood type without the Rh factor is classified as A negative (A-). This categorization is critical for blood transfusions, organ transplants, and pregnancy, as mismatched blood types can lead to severe immune reactions.

The other options do not accurately connect to the role of the Rh antigen. Blood viscosity refers to the thickness and stickiness of blood, which is influenced by various factors such as plasma proteins and hydration, rather than the Rh factor. The immune response to infections involves different components of the immune system, including white blood cells and antibodies, rather than the Rh antigen directly. Lastly, blood cell size is typically determined by genetic and developmental factors, not by the presence or absence of the Rh antigen.