Question 156·Hard·Boundaries
During solar eclipses, the temperature near the ground can drop noticeably. A recent study recorded a decrease of as much as 5 °C within _____ rapid cooling alters local wind patterns and briefly changes the direction of airflow.
Which choice completes the text so that it conforms to the conventions of Standard English?
For boundary questions, determine whether both sides of the blank are independent clauses. If so, eliminate options that use only a comma or no punctuation. When a conjunctive adverb (e.g., however, consequently, therefore) links the clauses, use a semicolon before it and a comma after it.
Hints
Check if the second part is a full sentence
Look at the words after the blank: does "this rapid cooling alters local wind patterns and briefly changes the direction of airflow" have its own subject and verb, or is it just a fragment?
Think about what kind of punctuation is needed
If both sides of the blank are complete sentences, ask: do we need a strong break (like a period or semicolon) or just a light pause (like a comma) between them?
Pay attention to the transition word
The word "consequently" is a transition between ideas. How is a transition like this usually punctuated when it comes between two complete sentences?
Eliminate options that cause comma errors
Cross out any choice that would leave only a comma—or no punctuation at all—between two full sentences, because that creates a comma splice or run-on.
Step-by-step Explanation
Identify the clauses
Consider the clauses on each side of the blank. The left clause is "A recent study recorded a decrease of as much as 5 °C within minutes," which has a subject ("A recent study") and a verb ("recorded"), so it is independent. The words after the blank begin another clause ("consequently, this rapid cooling alters local wind patterns and briefly changes the direction of airflow"), which has a subject ("this rapid cooling") and verbs ("alters," "changes"), so it is also independent.
Recall how to join independent clauses with a conjunctive adverb
Independent clauses can be joined by (1) a period, (2) a semicolon, or (3) a comma plus a coordinating conjunction. When a conjunctive adverb such as "consequently" is used between two independent clauses, standard usage calls for a semicolon before it and a comma after it.
Evaluate the choices by eliminating errors
Eliminate any option that leaves no punctuation between the clauses (run-on) or uses only a comma (comma splice). Also eliminate any option that fails to punctuate the conjunctive adverb correctly (it should be followed by a comma when it introduces the second clause).
Select the correct punctuation
Choose the option that places a semicolon before the conjunctive adverb and a comma after it: minutes; consequently, this.