People with at Least One Copy of the HLA-B53 Gene

People with at least one copy of the HLA-B53 gene are better able to beat back malarial infections before the infection progresses.If this is a coevolutionary arms race between Plasmodium and humans,what would the next step in this race be?

A) to see humans with more than one copy of the HLA-B53 gene
B) to see humans without the HLA-B53 gene
C) to see Plasmodium populations that counter the HLA-B53 gene
D) to see Plasmodium populations that have the HLA-B53 gene