Why (C) is right: offering an alternative cause
A Weaken explanation from our free library. The question below is original, written for this page. Then the full breakdown: why the right answer is right, and why each wrong answer is wrong.
The question
After the city lowered the speed limit on Maple Avenue, accidents there fell by 30 percent. The mayor concludes that the lower speed limit caused the drop.
Which one of the following, if true, most weakens the mayor's argument?
- Some drivers on Maple Avenue ignore the new speed limit.
- The 30 percent figure was calculated correctly by the city's statisticians.
- During the same period, the city repaved Maple Avenue and installed brighter streetlights. Correct
- Most Maple Avenue residents supported lowering the speed limit.
- The mayor has made road safety the centerpiece of her reelection campaign.
Why (C) is correct
The mayor sees one change, the new limit, and credits it with the result. Choice (C) points out two other changes that happened at the same time: new pavement and better lighting. Either one could explain fewer accidents on its own.
When a rival cause fits the same facts, the mayor's conclusion is no longer forced. The classic weaken move is exactly this: offer another story that explains the evidence.
Why the wrong answers are wrong
(A) Too weak to matter
The claim is about the overall accident rate, not about every driver. As long as enough drivers slowed down, the limit can still explain the drop. This does not break the causal story.
(B) True but irrelevant
Nobody disputed the number. The fight is about what caused it, and confirming the math does not answer that.
(D) Out of scope
Public support does not show the limit caused anything. Popularity and causation are different questions.
(E) Attacks the person
Her motives say nothing about whether the limit worked. Even a self-serving mayor can be right about the cause.
Last updated October 12, 2026