Chronic Fatigue Syndrome (CFS) Is a Debilitating Disease of Unknown

Chronic fatigue syndrome (CFS) is a debilitating disease of unknown etiology that is estimated to affect 17 million people worldwide. In a case-control observational study, researchers identified DNA from a human gamma-retrovirus (XMRV) in 68 of 101 patients with CFS (67%) compared with 8 of 218 healthy controls (3.7%) . We want to know if these data show evidence of a relationship between XMRV and CFS. Using significance level of 5%, what should you conclude?

A) There is significant evidence that XMRV causes CFS in a large fraction of the patients with CFS.
B) The data are consistent with the null hypothesis of no relationship between XMRV and CFS.
C) There is significant evidence of a relationship between XMRV and CFS, and XMRV is much more frequent among patients with CFS than would be expected if there was no such relationship.
D) You cannot conclude anything because the test assumptions are not met.