This July a group of 30 volunteers went to Kenya to help build a school and all of them took prophylaxis to prevent malaria. They claim that they took the medication as prescribed 2 weeks before, during their stay, and for 4 weeks after returning home. In October, one person developed malaria and by April of this year, 9 of the 30 volunteers had been treated for malaria. Which of the following is the least likely explanation for this apparent failure of prevention? A. This is most likely P. vivax or ovale which have a latent stage in their life cycle that persists in the liver and can result in disease weeks to months after exposure B. Most of the medication used for prophylaxis of malaria acts only on the red blood cell stage of the infection C. This could be P. malariae which is known to result in a more chronic malaria state D. This could be P. falciparum that was not completely treated by the prophylaxis E. The nine who got malaria must not have taken the medication as prescribed since this should have prevented malaria