Oxidizing Drugs Are an Effective Treatment for Malaria, but in Some

Oxidizing drugs are an effective treatment for malaria, but in some areas where the disease is especially prevalent, these drugs can be lethal. Why?

A) The mosquitoes that carry malaria in these areas have adapted to the drugs, are attracted by them, and so are more likely to infect and kill those people who take the drugs.
B) The parasite that causes malaria has become resistant to these drugs in some places, so is more likely to infect the people and kill them if they take the drugs.
C) People in these areas have adapted to resisting the malarial mosquitoes and the drugs compromise their resistance rather than helping.
D) People in these areas have adapted such that they naturally resist malaria using the same strategy as the drugs, so when they take the drugs, the extra oxidizing effect can kill them.
E) People in these areas have adapted to resist the effects of the malarial drug because they are already somewhat resistant to malaria as a result of being exposed to it a lot.