Students read passages presented in two font sizes. Researchers then measured average reading speed.

The claim under challenge is that the larger font substantially increased speed, and A directly contradicts that by reporting the actual, opposite direction of the small difference observed. B reports one condition's result in isolation, which cannot by itself challenge a comparative claim. C describes the font-size difference, not the resulting speed difference. D is true of both conditions but doesn't address the direction of the speed change.