When the human virus, hiv, first appeared, the mortality rate was close to 100%. however, recent information shows some individuals are unaffected by the virus. why is this not surprising?

Because of Mutation

Explanation:

Every individual has a different genetic makeup. Most of the individuals have traits that protect them from certain diseases. The resistance to HIV is seen in approximately 1% of the individuals. The resistance is the result of changes in the factors that contribute to the attachment of HIV to the cell.

An HIV virus needs a chemokine co-receptor CC5, for the entry in the cell. In some individuals, a mutation of CC5 is present and is known as  CCR5-Δ32 . This mutation doesn't allow the virus to enter the cell because it cannot attach itself to this receptor.

So, some individuals are not affected by HIV because of the mutation.

the answer is d its the most logical and accurate out of them all : )