John's conclusion is that "people evidently drive less safely near home than they do on long trips."
Why? Because in 80 percent of car accidents, the driver at fault was within five miles of home.
Judy, however, responds by explaining that the majority (i.e. 80 percent) of people do their driving within five miles of home. Thus, it is more likely that accidents will occur in the area where the most driving is done.
So, Judy's response explains that the statistic that John presents to prove his claim is not sufficient for his conclusion, i.e. answer choice (A): "it shows that the evidence that John presents, by itself, is not enough to prove his claim."
Hope that helped! Please let us know if you have any other questions.
