PT 47 S2 Q23

Until recently, biologists were unable to explain the fact that pathogens—disease-causing ... ...

Which one of the following, if true, would most seriously challenge the position of the biologists mentioned in line 13?
(A) Most pathogens capable of causing their hosts' deaths are able to achieve reproductive success.
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Practice Set: Science & Technology Mix 1