Question 86·200 Super-Hard SAT Reading Questions·Standard English Conventions
Mineral analyses, which were conducted at sites beyond the depression's rim and which, unlike earlier field _____ detected traces of basalt, do not by themselves establish that the depression is volcanic.
Which choice completes the text so that it conforms to the conventions of Standard English?
For questions involving long modifiers, first reduce the sentence to its grammatical core. Then examine each embedded clause for its own subject and verb, and check whether any supplementary phrase interrupts that core and therefore requires matching punctuation on both sides.
Hints
Find the core sentence
Temporarily remove the material between “analyses” and “do” to identify the subject and main verb.
Focus on the second relative clause
Determine the subject and verb in the portion beginning with the second occurrence of “which.”
Identify the interruption
Consider whether “unlike earlier field surveys” is essential to the grammatical core or interrupts it as supplementary information.
Step-by-step Explanation
Identify the main sentence
Temporarily remove the relative clause to reveal the main sentence: “Mineral analyses do not by themselves establish that the depression is volcanic.”
Examine the relative clause
The relative clause contains two coordinated parts: “which were conducted at sites beyond the depression's rim” and “which detected traces of basalt.” In the second part, “which” is the subject and “detected” is its verb.
Set off the interrupting phrase
The phrase “unlike earlier field surveys” interrupts the core construction “which detected traces of basalt.” The comma after “which” begins this supplementary phrase, so a matching comma after “surveys” closes it: “which, unlike earlier field surveys, detected traces of basalt.”