All of the above apply EXCEPT incomplete dominance.
multiple alleles - Blood type has three alleles (more than two): A, B, O
codominance - The A and B alleles are codominant to each other. Neither allele is dominant and both are expressed in the phenotype of the heterozygote (AB). In other words, individuals with blood type AB have the characteristics of both type A and type B blood.
principle of dominance - Both the A and B alleles are dominant to the O, which is recessive.
segregation of alleles - Alleles for blood type separate (orr segregate) during gametogenesis (gamete formation) and end up in different gametes, so that one allele is inherited from each parent.
(Note: Incomplete dominance is not demonstrated. It is also called partial dominance and is a form of intermediate inheritance in which one allele is not completely expressed over its paired allele. This results in a third phenotype in which the expressed trait is a combination of the phenotypes. In sum, one trait doesn't completely dominate over the other allele, thereby creating a new phenotype. This is not exhibited in blood types.)