Question 126·200 Super-Hard SAT Reading Questions·Expression of Ideas
Chemists developing a shorter synthesis of an anti-inflammatory compound repeatedly detected molecule L in the reaction mixture and therefore proposed that L was an intermediate on the route to the target compound. When the researchers prepared L separately and subjected it to the standard reaction conditions, however, it did not convert into the target. That failure alone was inconclusive: L might have required a short-lived reagent generated only while earlier steps were occurring. ______ isotope tracking showed that the atoms incorporated into the target had bypassed L, a result incompatible with L's proposed role.
Which choice completes the text with the most logical transition?
For difficult transition questions, compare not only the general direction of adjacent claims but also their relative scope, certainty, and evidentiary force. A broad additive transition may seem plausible, but a more precise transition is preferable when the text explicitly moves from tentative evidence to a stronger conclusion.
Hints
Compare evidentiary strength
Determine why the text calls the first finding inconclusive and how the isotope result differs from it.
Test each relationship
Ask whether the second finding is presented as parallel to the first, as contradicting the first, as an example of it, or as carrying greater evidentiary weight.
Step-by-step Explanation
Assess the first finding
L's failure to convert under the standard conditions casts doubt on the proposed pathway, but the text explicitly explains why this result is not conclusive: a necessary short-lived reagent might have been absent.
Assess the isotope evidence
The isotope tracking indicates that the atoms in the target did not pass through L. Unlike the first finding, this result is described as incompatible with L's being an intermediate in the proposed pathway.
Compare the findings
The second finding does not merely repeat, contradict, or illustrate the first. It provides stronger evidence against the proposed role, so “More decisively,” expresses the precise relationship.