题目选项分析

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?

【选项】The anopheles mosquito, which is the principal insect carrier of the malarial parasite, has been eradicated in many parts of the world.