A recent study of declining amphibian populations in the Pacific Northwest identified a troubling correlation between agricultural runoff and salamand...
GMAT Craft and Structure : (Structure) Questions
A recent study of declining amphibian populations in the Pacific Northwest identified a troubling correlation between agricultural runoff and salamander mortality rates. Researchers found that streams with elevated nitrate levels from nearby farms showed 40% fewer salamander species than comparable waterways in protected areas. Agricultural fertilizers containing high concentrations of nitrogen compounds migrate through soil into groundwater systems, eventually reaching stream environments where they disrupt aquatic food chains. This contamination pathway illustrates the far-reaching ecological consequences of modern farming practices on sensitive wildlife populations.
Which choice best describes the function of the underlined sentence in the text as a whole?
It provides information that helps support a claim about agricultural impact that is presented in the following sentence.
It contradicts the statistical findings presented in the previous sentence about species decline.
It introduces an alternative explanation for the phenomenon described in the opening sentence.
It summarizes the research methodology used to gather the data mentioned earlier in the passage.
Step 1: Decode and Map the Passage
Part A: Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "A recent study of declining amphibian populations in the Pacific Northwest identified a troubling correlation between agricultural runoff and salamander mortality rates." |
|
| "Researchers found that streams with elevated nitrate levels from nearby farms showed 40% fewer salamander species than comparable waterways in protected areas." |
|
| "Agricultural fertilizers containing high concentrations of nitrogen compounds migrate through soil into groundwater systems, eventually reaching stream environments where they disrupt aquatic food chains." |
|
| "This contamination pathway illustrates the far-reaching ecological consequences of modern farming practices on sensitive wildlife populations." |
|
Part B: Passage Architecture & Core Elements
Main Point: Agricultural runoff creates a contamination pathway that significantly reduces salamander populations by disrupting stream ecosystems.
Argument Flow: The passage starts with a research finding about the correlation between farm runoff and salamander mortality, provides specific statistical evidence, then explains the step-by-step mechanism by which fertilizers travel from farms to streams and disrupt food chains, concluding with the broader ecological significance of this contamination pathway.
Step 2: Interpret the Question Precisely
This is a fill-in-the-blank question asking us to choose the best logical connector. The answer must create the right relationship between what comes before and after the blank.
Step 3: Prethink the Answer
- Looking at our analysis, the underlined sentence comes right after we learn about the statistical correlation and provides the step-by-step mechanism explaining HOW fertilizers get from farms into streams
- Then the sentence immediately following says "This contamination pathway illustrates..." - referring back to the mechanism we just learned about
- So the underlined sentence provides the detailed explanation that the next sentence then refers to and builds upon
- The right answer should recognize that this sentence explains a process or provides information that supports or enables what comes next
It provides information that helps support a claim about agricultural impact that is presented in the following sentence.
✓ Correct
- This matches our analysis perfectly - the underlined sentence explains the contamination pathway mechanism
- The following sentence specifically refers to "this contamination pathway" and discusses its ecological consequences
- The underlined sentence provides the detailed information about how fertilizers migrate that supports the claim about "far-reaching ecological consequences" in the next sentence
It contradicts the statistical findings presented in the previous sentence about species decline.
✗ Incorrect
- The underlined sentence doesn't contradict anything about species decline
- It actually explains WHY there's species decline by showing the contamination mechanism
- The sentence works with the statistical findings, not against them
It introduces an alternative explanation for the phenomenon described in the opening sentence.
✗ Incorrect
- This isn't an alternative explanation - it's THE explanation for the phenomenon
- The opening sentence mentions a correlation, and this sentence explains the mechanism behind that same correlation
It summarizes the research methodology used to gather the data mentioned earlier in the passage.
✗ Incorrect
- The sentence describes a contamination process, not research methods
- It explains what happens to fertilizers, not how scientists studied the problem