Which of the following accurately describes the patterns of inheritance in human blood types?

The choices seem to be as follows:

a. Two alleles code for blood types and four phenotypes are possible.
b. Allele IA and IB are codominant, and allele i is recessive.
c. Allele i is dominant over alleles IA and IB.
D. Three alleles code for blood types and three phenotypes are possible. 

The answer to the question "Which of the following accurately describes the patterns of inheritance in human blood types" is A. Two alleles code for blood types and four phenotypes are possible. 

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