A punctuation question with a description near the blank tests where one full sentence ends. Read on both sides of the blank, including any describing phrases. A full sentence has its own subject and main verb and doesn't depend on another sentence. Two full sentences can be separated by a period, semicolon, or dash, or joined by a comma with a joining word. Then check what any earlier mark opens and whether it needs a matching closing mark.
Hints
- Hint 1
Find the subject and main verb before the dash. Do those words already form a full sentence?
- Hint 2
Read ahead to the project's main verb. The words about tissue regrowth come before it, so don't stop your sentence test there.
- Hint 3
Temporarily remove the axolotl description and the phrase about tissue regrowth. Check whether the remaining words can stand as separate sentences.
Step-by-step
Find the sentences, then handle the dash
Step 1Find the first full sentence
Start with Researchers recently sequenced the genome of the axolotl. The subject is Researchers, and the main verb is sequenced, which tells us what they did. These words can stand alone, so the first thought is a full sentence. The question is where that sentence ends once its description is included.
- Step 2
Read past the describing phrase
Read past shedding to the project may inform future medical therapies. Can this part stand alone? Yes: the project is the subject, and may inform is its main verb. The -ing phrase about tissue regrowth describes the project, but it doesn't join this full sentence to the one about the researchers. A second full sentence needs its own boundary.
- Step 3
Test the second dash
The dash in the axolotl—an amphibian opens an extra description. Would a second dash also separate the two sentences? No: after removing that description and the phrase about tissue regrowth, we'd still have the researchers' sentence followed by a comma and the project's sentence. That's a comma splice, meaning two full sentences joined by a comma alone. A pair of dashes doesn't create the needed sentence boundary.
- Step 4
End the sentence and its description
A description opened by a dash needs no closing dash when it ends with the sentence. The version limbs. Shedding uses that rule: the period ends both the description and the first sentence. Shedding light then introduces the project's sentence, with the existing comma after tissue regrowth, closing that opening phrase. Choice B.