B provides a fact that is believable and consistent with the stimulus, but the question is asking you to explain why higher congestion leads to less traffic accidents.

B just says moderate congestion has higher accidents, which doesn't explain anything about higher congestion.

I was going to say exactly this if someone hadn't said it already. If wild birds with small beaks are harder to capture, that would have always been true (unless told otherwise), and so the average wouldn't change.

#feedback