Which of the following, if true, suggests that the epidemiologist's plan for eliminating malaria is not viable? A. A person who is infected with malaria can infect a mosquito that is not carrying malaria, if that mosquito bites such a person. B. Unless a mosquito bites an infected person, and then bites a non-infected person, malaria cannot be passed directly from human to human. C. Malaria is still endemic in many parts of the world, and many health workers believe that the global eradication of malaria is not possible. D. Some people in areas where malaria is rife have developed an immunity to mosquitos, yet they also show a higher incidence of genetic disorders such as sickle-cell anemia. E. Mosquitos in many developing parts of the world are responsible for passing on a variety of viruses to human hosts.