Researchers studied four protected forests and recorded tree-species diversity (species count) along with two factors: presence of fire-management program (yes/no) and average forest age (young/old): Forest A, fire-mgmt + old, 88; B, fire-mgmt + young, 65; C, no fire-mgmt + old, 60; D, no fire-mgmt + young, 42. The researchers argued that fire management has a roughly equal positive effect on diversity regardless of forest age. The strongest support is ______
Which choice most logically completes the text using the data above?
- A
Forest D's lowest diversity of 42.
- B
Forest A's highest diversity of 88.
- Ccheck_circle
the within-age contrasts: A vs. C (both old: 88-60=28) and B vs. D (both young: 65-42=23)—fire management adds about the same number of species in both age groups.
- D
the average across forests.
Explanation
"Roughly equal effect regardless of age" requires showing similar fire-mgmt-driven gains within each age stratum. Choice B captures this similarity (28 vs. 23 species) directly.