In a certain state, the rate at which inhabitants of City X contract a certain disease is significantly lower than the rate at which inhabitants of City Y contract the disease. So if a couple originally from City Y relocates to City X and raises a family there, their children will be significantly less likely to contract this disease than they would had they remained in City Y.
Which of the following, if true, would most seriously weaken the conclusion drawn in the passage?
A. Many health experts do not believe that moving to City X will lead to a significant increase in the average person’s immunity to the disease.
B. The mayor of City Y has falsely claimed that statistics relating to the incidence of the disease in his city are not accurate.
C. The lower incidence of the disease in City X can be ascribed mostly to genetically determined factors.
D. Some inhabitants of City Y possess a greater immunity to the disease than do the healthiest inhabitants of City X.
E. Smog levels in City X are significantly lower than those of any other city in the state.