A punctuation question tests how sentence parts fit together when choices change marks or joining words. Split the text at the blank, looking past any opening description for a subject and verb. Ask whether each side can stand alone. Two full sentences need a period, a semicolon, or a comma plus a joining word; a colon also needs the second part to explain the first. A pause in your voice isn't enough to tell you which mark the sentence needs.
Hints
- Hint 1
Read past the opening description and find who or what each part is about and its verb.
- Hint 2
The and before the blank belongs to the pair introduced by both. Look for where that pair ends and a new subject begins.
- Hint 3
Compare the fact about Chicago with the fact about its streets. Ask how the two parts are related, rather than deciding by where you'd pause.
Step-by-step
Find the full sentences and test the join
Step 1Look past the opening description
The opening Growing rapidly in the late nineteenth century, describes Chicago, so let's look past it to test the join at the blank. Who does what? The words Chicago became give us the subject and main verb, telling who the sentence is about and what happened. The and in both industry and links two nouns, so the missing noun completes the first full sentence.
- Step 2
Test the words after the blank
Can the words after the blank stand alone? many of the city’s streets is the subject, and were laid out is its main verb. Those words tell us something complete about the streets, so the second part is also a full sentence.
- Step 3
Check what the second sentence adds
Does the street layout explain Chicago's role as a hub? A colon needs more than two complete sentences: the second must explain or add detail to the first. Being laid out in a grid describes the streets, not Chicago's role in industry and culture. The street sentence adds a separate fact, so the version with a colon doesn't give these ideas the right link.
- Step 4
Give the join both parts
Before many of the city’s streets, a comma and and must work as a pair to join the full sentences. The version with and alone leaves out the comma, while the semicolon version replaces the comma needed before and here. A semicolon normally joins full sentences without a joining word. culture, and gives us both parts of the needed pair. Choice D.