Question 91·200 Super-Hard SAT Reading Questions·Expression of Ideas
While researching chemical signaling among plants, a student has taken the following notes:
- Sagebrush leaves damaged by herbivores release airborne compounds, and nearby undamaged plants may respond by increasing their production of defensive chemicals.
- Researchers hypothesized that one compound, methyl jasmonate, causes this response rather than a signal transmitted through shared soil.
- The researchers placed plants from the same genetic line in separate pots whose soil and roots were enclosed to prevent belowground exchange. All plants were kept under the same light and temperature conditions.
- Air from a damaged source plant was directed toward an undamaged plant either without alteration or after passing through an activated-carbon filter. The airflow rate was the same in both conditions.
- Activated carbon removes many airborne compounds, including methyl jasmonate.
- Plants receiving unfiltered air increased their defensive chemicals, whereas plants receiving filtered air did not.
The student wants to explain how the experimental design strengthens the causal case for airborne signaling over belowground signaling while also identifying why the result does not establish that methyl jasmonate specifically caused the response. Which choice most effectively uses relevant information from the notes to accomplish this goal?
For a rhetorical-synthesis question about causal evidence, first identify what the design holds constant and what it deliberately changes. Then determine the broad causal conclusion supported by the outcome and distinguish that conclusion from a more specific claim the experiment cannot isolate. Evaluate every option against both parts of the student's stated goal, watching for choices that correctly identify the general causal route but overstate which component was responsible.
Hints
Separate the two requirements
Look for a choice that addresses both the route by which the signal traveled and the limits of identifying a particular compound.
Examine what was controlled
Consider what enclosing the roots and soil rules out and what passing the air through a filter changes.
Evaluate the filter's specificity
Ask whether removing several possible causes at once can establish which individual cause was responsible.
Step-by-step Explanation
Identify both parts of the goal
The response must explain why the experiment favors airborne signaling over belowground signaling and why the findings do not establish that one particular airborne compound caused the response.
Interpret the experimental controls
The plants' roots and soil were enclosed, preventing belowground exchange. Light, temperature, and airflow rate were also controlled, while the researchers varied whether air from the damaged plant was filtered.
Connect the outcomes to the causal account
Only plants receiving unfiltered air increased their defensive chemicals. Since belowground exchange was blocked, this contrast supports the claim that something carried through the air caused the response.
Determine what the filter cannot establish
Activated carbon removed methyl jasmonate along with many other airborne compounds. Therefore, the experiment implicates airborne signaling but cannot determine whether methyl jasmonate, another compound, or some combination of compounds produced the response.