Biologists studied four river restoration sites and recorded macroinvertebrate diversity (species count) along with two factors: pollution-source removal (yes/no) and riparian buffer planting (yes/no): Site A, both interventions, 92 species; B, pollution removal only, 48; C, buffer only, 38; D, neither, 22. The researchers argued <em>both</em> interventions independently boost diversity, with pollution removal showing the larger effect. The strongest support is ______
Which choice most logically completes the text using the data above?
- A
Site D's lowest count of 22.
- Bcheck_circle
the comparison: pollution-removal effect (A vs. C: 92-38=54 species; B vs. D: 48-22=26 species) versus buffer effect (A vs. B: 92-48=44 species; C vs. D: 38-22=16 species)—pollution removal adds more species (26-54) than buffer plantings (16-44) in matched comparisons.
- C
the average across sites.
- D
Site A's highest count of 92.
Explanation
To argue both interventions matter independently and pollution removal is larger, examine each variable while holding the other constant. Choice B does both pairs of comparisons and shows pollution removal has slightly larger effects (26-54 species) than buffer planting (16-44 species).