PT 60 S1 Q5

Recent epidemiological studies report that Country Xhas the lowest incidence ... ...

Which one of the following, if true, most helps to resolve the apparent discrepancy described above?
(A) There are several forms of disease P, some of which are more contagious than others.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Complete Section: LR-A, June '10 LSAT (PT 60 Sec. 1)