@dfolave the flaw here is that the author is overlooking any possible overlaps between the two groups presented.
This is the data the columnist sets forth:
(1) More than 25% of traffic accidents involving bicycles are caused by the failure of bicyclists to obey traffic regulations.
(2) More than 25% of traffic accidents involving bicycles are caused by inadequate bicycle safety equipment.
From this data, the columnist concludes, "bicyclists are at least partially responsible for more than half of the traffic accidents involving bicycles." So basically the columnist is adding these two groups together (more than 25% + more than 25% = more than 50%).
The flaw here is that it is possible that these two groups overlap, i.e. some traffic accidents involving bicycles involved both failure of bicyclists to obey traffic regulations AND inadequate bicycle safety equipment.
This is what (C) is explaining, i.e. "fails to consider the possibility that more than one factor may contribute to a given accident."
More than one factor here means both failure of bicyclists to obey traffic regulations AND inadequate bicycle safety equipment.
Hope this helps! Please let us know if you have any other questions.
