Economists studied four cities and reported median commute time (min) along with two factors: density (high/low) and quality of transit (high/low): City A, high density + high transit, 21 min; B, high density + low transit, 38; C, low density + high transit, 28; D, low density + low transit, 35. The researchers argued that good transit reduces commute time more strongly in high-density cities. The strongest support is ______
Which choice most logically completes the text using the data above?
- A
the average commute.
- B
City D's commute of 35 min.
- C
City A's commute of 21 min.
- Dcheck_circle
the within-density contrasts: A vs. B saves 17 min (38→21), while C vs. D saves only 7 min (35→28)—transit's benefit is much larger in high-density cities.
Explanation
"Stronger in high-density cities" requires comparing transit's effect within each density stratum. Choice B does this and shows the 17-min vs. 7-min difference, supporting the differential effect claim.