Question 206·Medium·Boundaries
In her groundbreaking 2018 study, Dr. Amara Patel concluded that ____ was no longer the sole determinant of coral bleaching events, emphasizing the influence of nutrient pollution and disease.
Which choice completes the text so that it conforms to the conventions of Standard English?
For punctuation-boundary questions, first strip the sentence down to its core subject and verb to see what must stay together (here, "temperature … was"). Then identify any extra, nonessential information that interrupts that core; such phrases must be set off on both sides with matching punctuation (commas, dashes, or parentheses). Quickly eliminate any choice that uses no punctuation, only a single mark, or mismatched marks around the interrupting phrase, and select the option that both encloses the extra information correctly and leaves the main sentence clear when that information is removed.
Hints
Find the main sentence without the middle phrase
Ignore the words "long considered the only variable" and read the sentence with just "temperature" in the blank. What are the subject and verb?
Decide what kind of information the middle words give
Ask yourself whether "long considered the only variable" is essential to identifying what temperature is, or if it is extra description that can be removed without breaking the sentence.
Think about punctuation around extra information
When extra information interrupts the subject and verb, what must you put on both sides of that information? Look for an answer that uses matching punctuation marks to enclose the phrase.
Check for symmetry and consistency
Eliminate any option that uses no punctuation, only one mark, or different marks (like a dash on one side and a comma on the other) around the same interrupting phrase.
Step-by-step Explanation
Find the core sentence
Ignore the extra descriptive phrase for a moment and focus on the main idea:
- Core structure: "Dr. Amara Patel concluded that ___ was no longer the sole determinant of coral bleaching events."
The blank should contain the subject that goes with the verb "was." That subject is "temperature." The phrase "long considered the only variable" is extra information about "temperature."
Identify the type of phrase in the middle
The words "long considered the only variable" describe "temperature" but are not essential to the basic meaning of the sentence. If you remove them, the sentence still makes sense:
- "…concluded that temperature was no longer the sole determinant of coral bleaching events…"
Because this is nonessential, interrupting information placed between the subject ("temperature") and the verb ("was"), it must be set off on both sides with matching punctuation: either commas, dashes, or parentheses.
Eliminate choices that don’t properly set off the phrase
Check how each option punctuates the phrase "long considered the only variable":
- A) has no punctuation around the phrase, so the extra information is not set off at all.
- B) has one comma before the phrase but none after it, so the nonessential phrase is not enclosed on both sides.
- C) has a dash before the phrase and a comma after it, which mixes punctuation marks instead of using a matching pair.
All of these violate the rule that a nonessential interrupting phrase must be enclosed by matching punctuation marks.
Choose the option with matching punctuation that keeps the sentence smooth
The remaining option uses a dash before and a dash after the interrupting phrase, neatly enclosing the nonessential information and keeping the core sentence intact:
- "…concluded that temperature—long considered the only variable— was no longer the sole determinant of coral bleaching events…"
This correctly sets off the extra phrase with a matching pair of dashes, so the correct answer is temperature—long considered the only variable—.