A punctuation question with a short word after the blank tests where one full sentence ends and another begins. Split at the blank and find each side’s subject: who or what it’s about. Then find its main verb, which tells what the subject does or is, and ask whether each side can stand alone. Two full sentences need a complete join: a period, a semicolon, or a comma plus a joining word such as and. Don’t choose punctuation by where you’d pause.
Hints
- Hint 1
Look for Priya Nair’s main verb before the blank. Which verb tells what she did, rather than what the purifier does?
- Hint 2
Then read the words starting with she as a separate sentence. Do they have a subject and main verb, or do they need the earlier words to be complete?
Step-by-step
Split and test both sides
Step 1Test the first side
Split after backpack, the word shared by the choices, to test what kind of join we need. In engineer Priya Nair demonstrated a solar-powered water purifier, who did what? Priya Nair is the subject, who the sentence is about, and demonstrated is the main verb, which tells what she did. The description of where the purifier fits doesn’t change that, so the first side can stand alone.
- Step 2
Test the words after the blank
Can she then invited students to test the device outdoors stand alone too? She is the subject, and invited is its main verb. Even though she refers back to Priya Nair, those words form a full sentence, so we’re joining two full sentences.
- Step 3
Supply the complete join
How should we join the purifier description to she then invited students? A period or a semicolon can join full sentences on its own, while a comma needs a joining word such as and. With and, the comma and joining word must come together. The version backpack, and has both. Choice A.