A new traffic light system was installed at a busy intersection, and in the following month, the number of accidents at that intersection decreased by 20%. City officials claim the new system is effective in improving road safety. Which of the following, if true, would most strengthen the city officials' claim?
✓ Correct Answer: Option A
This option provides a control group for comparison. If other intersections without the new system saw no change, it suggests the reduction at the treated intersection is indeed attributable to the new system, strengthening the claim. Difficulty: 3