A punctuation question with the same transition in every choice tests where sentences end. Cover the transition and check whether each side can stand alone, because a transition can't join full sentences by itself. Decide which sentence the transition belongs to. An opening transition takes a comma after it; an ending transition takes one before it; one in the middle takes commas around it. Between full sentences, use a period or semicolon, since commas alone can't separate them.
Hints
- Hint 1
Cover therefore and test whether each side can stand alone. Find who does what on each side.
- Hint 2
Look for how the discovery and the scientists’ response are linked.
- Hint 3
After deciding which sentence therefore belongs to, check the punctuation on both sides of it.
Step-by-step
Cover, split, and place the transition
Step 1Test each side of the blank
Cover therefore and add flower, which every choice includes, to see whether the blank falls between full sentences. Before the blank, Dr. Lena Nguyen announced has a subject and a main verb: it tells us who did something and what she did. Can the words after the blank stand alone too? scientists began reconsidering previous timelines also has its own subject and main verb. Both sides express complete thoughts, even with the longer descriptions attached.
- Step 2
Separate the full sentences
What can separate these full sentences? A transition such as therefore shows how ideas relate, but it can't join full sentences, so we need a period or semicolon. The version flower, therefore, leaves a comma splice, two full sentences joined only by a comma, before scientists began reconsidering previous timelines. The version flower therefore, leaves no mark before the transition, and the comma after it doesn't properly separate the sentences.
- Step 3
Check the transition’s comma
An opening transition needs a comma after it to set it off from its sentence. The version flower; therefore leaves out that comma before scientists began reconsidering previous timelines, so the opening word runs into the rest of the sentence.
- Step 4
Place the transition with the result
Which sentence gives the result of the discovery? scientists began reconsidering previous timelines describes what the discovery led them to do. Therefore means as a result, so it belongs at the start of that second sentence, with a semicolon before it and a comma after it: flower; therefore,. Choice A.