A 2022 study compared four wetland sites' frog populations along with two factors: presence of road runoff (yes/no) and water acidity (high/low pH): Site A, no runoff + low acidity, 540 frogs; B, no runoff + high acidity, 320; C, runoff + low acidity, 220; D, runoff + high acidity, 90. The researchers argued road runoff and water acidity <em>both</em> harm frogs and that runoff's effect is similar in magnitude across acidity levels. The strongest support is ______
Which choice most logically completes the text using the data above?
- A
Site A's highest count of 540.
- B
the average count across sites.
- Ccheck_circle
the within-acidity contrasts: A vs. C (low acidity: 540-220=320 frogs lost to runoff) and B vs. D (high acidity: 320-90=230 frogs lost to runoff)—runoff penalty is large at both acidity levels.
- D
Site D's count of 90.
Explanation
To argue runoff's effect is similar across acidity levels, compare runoff's effect within each acidity stratum. Choice B captures both within-acidity comparisons (320 and 230 frogs lost) and shows runoff matters at both acidity levels.