Final answer:
Serologic tests determine a person's phenotype, such as their blood type.
Step-by-step explanation:
Serologic tests determine a person's phenotype. These tests are used to detect antibodies or antigens in a person's blood. For example, serologic tests can determine a person's blood type, which is classified into four types: Type A, Type B, Type AB, and Type O. Each type has a different phenotype based on the presence or absence of certain antigens.