Answer:
A) AIDS.
Step-by-step explanation:
AIDS stands for Acquired Immune Deficiency Syndrome, like its name says, this syndrome alters the immune system in such a hard way that even a simple flu can kill you, because you don't haven any defences to fight against.
This syndrome is so heavy and complicated, imagine that AIDS can mutate according with DNAs, this means that the virus information is different in each individual.