Critical Reasoning

Red blood cells in which the malarial-fever parasite resides are eliminated from a person's body after 120 days. Because the parasite cannot travel to a new generation of red blood cells, any fever that develops in a person more than 120 days after that person has moved to a malaria-free region is not due to the malarial parasite.

Which of the following, if true, most seriously weakens the conclusion above?

(A) The fever caused by the malarial parasite may resemble the fever caused by flu viruses.

(B) The anopheles mosquito, which is the principal insect carrier of the malarial parasite, has been eradicated in many parts of the world.

(C) Many malarial symptoms other than the fever, which can be suppressed with antimalarial medication, can reappear within 120 days after the medication is discontinued.

(D) In some cases, the parasite that causes malarial fever travels to cells of the spleen, which are less frequently eliminated from a person's body than are red blood cells.

(E) In any region infested with malarial-carrying mosquitoes, there are individuals who appear to be immune to malaria.

To weaken a conclusion, we don't have to disprove it, but only to make it less convincing. The right answer should suggest a way that a person who has been in a malaria-free region for over 120 days can still get a malaria-induced fever. Note that the premise tells us that the parasite cannot go from one generation of red blood cells to the next, but the argument doesn't block other ways that the parasite can stay in the body.

The answer is D. I go through the question in detail in the full solution below (taken from the GMATFix App).



-Patrick