Question 21·Hard·Boundaries
During the 2018 field season, marine biologists observed an unexpected increase in coral spawning _____ therefore, these findings suggest that some reefs may be more resilient to warming oceans than previously thought.
Which choice completes the text so that it conforms to the conventions of Standard English?
First determine whether each side of the blank is an independent clause. If the second clause starts with a conjunctive adverb (e.g., however, therefore, consequently), use a semicolon before the adverb and a comma after it to keep one sentence. Eliminate choices that create comma splices, misuse colons, or mishandle capitalization after a period.
Hints
Check both sides of the blank
Ensure the words before and after the blank can each form a complete sentence (subject + verb) once the missing word is supplied.
Spot the conjunctive adverb
Notice the second clause begins with "therefore"—a conjunctive adverb. Think about the punctuation that properly introduces such a clause.
Avoid common boundary errors
A single comma cannot join two complete sentences; after a period, the next word must be capitalized; a colon should introduce a list or direct explanation, not a conjunctive adverb.
Step-by-step Explanation
Identify the clause structure
Completing the first clause with the word from the choices gives: "During the 2018 field season, marine biologists observed an unexpected increase in coral spawning events." The second clause begins with a conjunctive adverb: "therefore, these findings suggest that some reefs may be more resilient to warming oceans than previously thought." Both are independent clauses.
Recall the rule for conjunctive adverbs
When a second independent clause starts with a conjunctive adverb (e.g., therefore, however, consequently), join the clauses with a semicolon before the adverb and place a comma after the adverb.
Test each option against the rule
- A comma before "therefore" leaves two independent clauses joined by only a comma, which is a comma splice.
- A colon is used to introduce a list or a direct explanation of what was just announced; it is not used to precede a conjunctive adverb linking two full clauses.
- A period would start a new sentence, which would require "Therefore" to be capitalized.
- A semicolon before "therefore" and a comma after it correctly connects the clauses in one sentence.
Select the best choice
The only option that correctly applies the conjunctive-adverb rule and maintains one sentence is "events; therefore, these."