Step 1: Understanding the Concept:
This is a critical reasoning question. We need to evaluate Gary's argument. Gary's argument is a classic example of a "post hoc ergo propter hoc" (after this, therefore because of this) fallacy. He observes that accidents increased after the modification and concludes that the modification \textit{caused} the increase. To evaluate this argument, we must consider other potential causes for the increase in accidents.
Step 2: Detailed Explanation:
Gary's argument structure:
Premise: After the modification, the number of accidents per week increased.
Conclusion: Therefore, the modification caused the increase in accidents.
This argument is weak because it fails to consider alternative explanations. A strong evaluation would involve investigating other factors that could have led to an increase in accidents.
Let's analyze the options:
(A) The severity of accidents (personal injury) is a different issue from the frequency of accidents. This information would not help evaluate Gary's claim about the \textit{likelihood} of accidents increasing.
(B) The tenure of the traffic commission members is irrelevant to the causal relationship between the modification and the accident rate.
(C) Public approval of the commission is irrelevant to the factual cause of the increased accident rate.
(D) Measures taken in nearby towns are irrelevant to the causes of accidents at this specific intersection in this town.
(E) This is a crucial question. If the volume of traffic at the intersection has significantly increased over the past three years, then an increase in the number of accidents might be expected, regardless of the modification. It's possible the modification actually \textit{decreased} the accident \textit{rate} (accidents per car), but the sheer increase in the number of cars led to a higher total number of accidents. This information is essential to determine whether the modification was a failure or if other factors were at play.
Step 3: Final Answer:
To properly evaluate Gary's claim that the modification caused more accidents, it is essential to know if another variable, such as traffic volume, has changed. An increase in traffic volume is a very strong alternative explanation for an increase in the number of accidents.