Question 39·Hard·Boundaries
In February 2020, Dr. Lena Nguyen announced her team's discovery of a fossilized _____ scientists began reconsidering previous timelines for the evolution of angiosperms, suggesting that flowering plants appeared millions of years earlier than scientists once believed.
Which choice completes the text so that it conforms to the conventions of Standard English?
For boundary questions, first determine whether the text before and after the blank can each stand alone as a complete sentence once a choice is inserted. If they are two independent clauses and the second begins with a conjunctive adverb such as “therefore,” the standard pattern is a semicolon between the clauses and a comma after the conjunctive adverb. Then eliminate choices that create a comma splice or omit required punctuation.
Hints
Plug in each choice and check for complete sentences
Try each option in the blank. After you fill it in, ask: is the part before the boundary a complete sentence, and is the part after it also a complete sentence?
Notice “therefore”
“Therefore” is a conjunctive adverb. In formal writing, when it connects two complete sentences, it is usually preceded by a semicolon and followed by a comma.
Avoid weak joins
If both sides are complete sentences, a comma by itself is not strong enough to join them (that would be a comma splice).
Step-by-step Explanation
Read the sentence with each choice in the blank
The blank falls where one clause ends and the next begins. After inserting a choice, check whether you have two complete sentences (independent clauses) on either side of the boundary.
Identify the two independent clauses
First clause (with the necessary words filled in):
"In February 2020, Dr. Lena Nguyen announced her team's discovery of a fossilized flower"
This has a subject (Dr. Lena Nguyen) and a verb (announced), so it is an independent clause.
Second clause:
"scientists began reconsidering previous timelines for the evolution of angiosperms..."
This has a subject (scientists) and a verb (began), so it is also an independent clause.
Use the standard pattern with a conjunctive adverb
When a conjunctive adverb like “therefore” connects two independent clauses in one sentence, the standard convention is:
- a semicolon between the clauses, and
- a comma after the conjunctive adverb
So the correct structure is: independent clause; therefore, independent clause.
Match the rule to the choices
Only flower; therefore, correctly places a semicolon between the two independent clauses and includes the comma after “therefore.”
So the correct answer is flower; therefore,.