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?
a) individuals started to use protective measures more frequently.
b) the virus mutated through natural selection.
c) humans are genetically diverse, and some are immune to the virus.
d) new pharmaceutical medicines were produced that were more effective.

The correct answer is C) Humans are genetically diverse, and some are immune to the virus.

Explanation:

Human Immuno virus is the virus that is responsible for causing a deadly disease called AIDS in humans. When this virus has first appeared the mortality rate was close to 100% but now it is found that some people are not affected by this virus because they have some variation in their genome which does not allow the HIV to infect immune cells.

Some humans have mutated CCR5 gene and CCR5 gene plays an important role in HIV entry in the immune cell. These individuals with mutated CCR5 gene do not allow the entry of the HIV in the immune cell and protect these people from HIV infection. So some humans are immune to the HIV therefore the right answer is C.