# SAT punctuation: Boundaries questions

Canonical: https://duckyhelper.com/learn/sat-reading-writing/boundaries-punctuation/
Updated: 2026-10-01

Boundaries questions test where sentences start and stop. First decide whether the words on each side of the blank are a complete sentence. Two complete sentences need a period, a semicolon, or a comma plus and, but or so; a comma alone is an error. A colon must follow a complete sentence. Extra information needs a matching pair of commas. Between a subject and its verb, use no punctuation.

## What the question looks like

Boundaries is one of two skills in **Standard English Conventions**. College Board says these questions ask you to edit text so sentences are conventionally complete: end punctuation, semicolons and colons, and when to use or not use commas, dashes and parentheses to set off information. The stem is *Which choice completes the text so that it conforms to the conventions of Standard English?* The four choices usually show the same words with different punctuation.

## The one test that solves most questions

Cover the choices. Ask: is the part before the blank a complete sentence (an **independent clause**: a subject plus a verb that can stand alone)? Is the part after it? Then use this table.

**What can go between two parts**

| Left side | Right side | Allowed | Not allowed |
| --- | --- | --- | --- |
| Complete sentence | Complete sentence | period; semicolon; comma + and/but/so/or/yet/for/nor; colon if the right side explains the left | comma alone (comma splice); nothing (run-on) |
| Complete sentence | List, example or explanation (not a sentence) | colon; comma if it is a natural add-on | semicolon |
| Dependent clause (starts with *because*, *although*, *when*...) | Complete sentence | comma | semicolon, period |
| Subject | Its verb | nothing | any single comma, colon or semicolon |

## The rules with right and wrong examples

| Rule | Wrong | Right | Why |
| --- | --- | --- | --- |
| No comma splices | *The storm passed, the streets were flooded.* | *The storm passed; the streets were flooded.* | Two complete sentences cannot be joined by a comma alone. |
| However and therefore are not joining words | *The test was hard, however, most students passed.* | *The test was hard; however, most students passed.* | *However* is a transition, not a conjunction. The two sentences still need a semicolon or period. |
| A colon needs a complete sentence before it | *The kit includes: a map, a compass, and a whistle.* | *The kit includes three items: a map, a compass, and a whistle.* | *The kit includes* is not complete; it needs its object. Add a full sentence before the colon. |
| Extra information takes a matching pair | *Ada Lovelace, the daughter of Lord Byron wrote notes on Babbage's engine.* | *Ada Lovelace, the daughter of Lord Byron, wrote notes on Babbage's engine.* | Open with a comma, close with a comma. Two long dashes or two parentheses also work, but never mix types. |
| No punctuation between subject and verb | *The students who finished early, went outside.* | *The students who finished early went outside.* | The subject is *the students who finished early*. Nothing goes between it and *went*. |
| Essential names take no commas | *The poet, Joy Harjo, served as US Poet Laureate.* | *The poet Joy Harjo served as US Poet Laureate.* | There are many poets, so the name is needed to say which one. Needed information is not set off. |

## Worked examples

**Example 1: two complete sentences**

Problem: The town's oldest bridge opened in ______ it still carries thousands of cars each day. Which choice completes the text so that it conforms to the conventions of Standard English? Choices: 1883, / 1883; / 1883 / 1883, and,

1. Left side: *The town's oldest bridge opened in 1883.* Complete.
2. Right side: *it still carries thousands of cars each day.* Also complete.
3. Two complete sentences: a semicolon works. A comma alone is a splice, nothing is a run-on, and *and,* with a comma after it puts a comma where none belongs.

Answer: 1883;

**Example 2: a transition in the middle**

Problem: The museum's new wing was finished in ______ it will not open to visitors until the fall, when the paintings arrive. Choices: March; however, / March, however, / March, however; / March however

1. Find the two sentences: *The museum's new wing was finished in March.* and *it will not open to visitors until the fall.*
2. *However* belongs to the second sentence, so the strong mark goes before it: semicolon, then *however*, then a comma.
3. *March, however,* is a comma splice. *March, however;* attaches *however* to the wrong sentence. No punctuation is a run-on.

Answer: March; however,

**Example 3: close the pair**

Problem: Ada Lovelace, the daughter of the poet Lord ______ wrote notes on Charles Babbage's Analytical Engine that included what many consider the first computer program. Choices: Byron, / Byron / Byron; / Byron:

1. Spot the comma after *Lovelace*. It opens extra information: *the daughter of the poet Lord Byron*.
2. Extra information must be closed with the same mark, so a comma goes after *Byron*.
3. With no comma, the pair is never closed. A semicolon or colon would split the subject *Ada Lovelace* from its verb *wrote*.

Answer: Byron,

## Common mistakes and fixes

| Mistake | Fix |
| --- | --- |
| Choosing a comma because there is a pause | Pauses are not rules. Check for complete sentences on both sides. |
| Treating *however* like *but* | *But* can join sentences with a comma. *However*, *therefore* and *moreover* cannot. |
| Putting a colon after *includes*, *such as* or *are* | The words before a colon must be a complete sentence on their own. |
| Opening extra information with a comma and closing with a long dash | Match the pair: comma and comma, dash and dash, parenthesis and parenthesis. |
| Adding a comma after a long subject | Find the main verb and make sure nothing separates it from its subject. |

> **Tip: Semicolon equals period**
>
> On the SAT, a semicolon between clauses works like a period. If you could not put a period there, you cannot put a semicolon there.

## Practice

**Five Boundaries questions**

1. Honeybees beat their wings about 200 times per ______ this rapid motion produces their familiar buzzing sound. Which choice completes the text so that it conforms to the conventions of Standard English?
   A. second and,
   B. second, and
   C. second,
   D. second

   Answer: second, and. Both sides are complete sentences, so they need a comma plus a joining word like *and*. *And,* with the comma after it is wrong, a comma alone is a comma splice, and nothing at all is a run-on.

2. The recipe calls for only three ______ flour, water, and salt. Which choice completes the text so that it conforms to the conventions of Standard English?
   A. ingredients, such as:
   B. ingredients;
   C. ingredients
   D. ingredients:

   Answer: ingredients:. *The recipe calls for only three ingredients* is complete, and a list follows, so a colon is right. A semicolon needs a full sentence after it. No punctuation runs the list into the noun. A colon after *such as* breaks the rule that a colon follows a complete sentence.

3. Mount ______ known in Nepal as Sagarmatha, rises about 8,849 meters above sea level. Which choice completes the text so that it conforms to the conventions of Standard English?
   A. Everest;
   B. Everest
   C. Everest,
   D. Everest:

   Answer: Everest,. *known in Nepal as Sagarmatha* is extra information, and it is already closed with a comma after *Sagarmatha*. It must open with a comma too. A semicolon or colon would cut the subject *Mount Everest* off from its verb *rises*.

4. Solar panels produce no electricity at ______ many homes with solar panels also have batteries that store power for the evening. Which choice completes the text so that it conforms to the conventions of Standard English?
   A. night, therefore,
   B. night therefore,
   C. night; therefore,
   D. night, therefore;

   Answer: night; therefore,. There are two complete sentences, and *therefore* begins the second. Use a semicolon before it and a comma after it. A comma before *therefore* is a comma splice, no mark at all is a run-on, and *night, therefore;* attaches *therefore* to the first sentence.

5. The marine ______ Rachel Carson published *Silent Spring*, a book about the dangers of pesticides, in 1962. Which choice completes the text so that it conforms to the conventions of Standard English?
   A. biologist
   B. biologist,
   C. biologist:
   D. biologist;

   Answer: biologist. The name tells which marine biologist, so it is essential and takes no commas. A single comma would open extra information that is never closed. A colon or semicolon would split the subject from the verb *published*.

## Frequently asked questions

### What is the difference between Boundaries and Form, Structure, and Sense?

Both are in Standard English Conventions. Boundaries is about punctuation between and inside sentences: semicolons, colons, commas, run-ons. Form, Structure, and Sense is about word forms: subject-verb agreement, pronouns, verb tense, modifiers and possessives. See [form, structure, and sense](https://duckyhelper.com/learn/sat-reading-writing/form-structure-and-sense/).

### Does the SAT test dashes?

Yes. College Board lists dashes with commas and parentheses as ways to set off information. A pair of long dashes works like a pair of commas, and a single long dash can introduce an explanation like a colon. The rule that trips students up is mixing: never open with a comma and close with a dash.

### Is a comma before and always needed between two sentences?

In formal writing, put a comma before *and*, *but* or *so* when it joins two complete sentences. Some style guides let very short, closely linked clauses skip it, but on a test the comma plus the joining word is the safe, standard choice. Never put the comma after the joining word instead.

### How can I check a semicolon fast?

Cover the semicolon and read each side alone. If both sides are complete sentences, the semicolon can work. If either side is a fragment, like *because it rained* or *such as maps*, the semicolon is wrong.

## Sources

- [College Board, Assessment Framework for the Digital SAT Suite, version 3.01 (August 2024)](https://satsuite.collegeboard.org/media/pdf/assessment-framework-for-digital-sat-suite.pdf), accessed 2026-10-01
- [Purdue OWL, Commas vs. Semicolons](https://owl.purdue.edu/owl/general_writing/punctuation/commas/commas_vs_semicolons.html), accessed 2026-10-01
- [Purdue OWL, Commas: Quick Rules](https://owl.purdue.edu/owl/general_writing/punctuation/commas/index.html), accessed 2026-10-01

## Related

- [When to use a semicolon](https://duckyhelper.com/learn/grammar/semicolons/)
- [Run-on sentences, comma splices and fragments](https://duckyhelper.com/learn/grammar/run-on-sentences-and-fragments/)
- [SAT grammar: Form, Structure, and Sense](https://duckyhelper.com/learn/sat-reading-writing/form-structure-and-sense/)
- [SAT Reading and Writing study guides](https://duckyhelper.com/learn/sat-reading-writing/)

## Try asking Ducky

- "I keep mixing up semicolons and colons on practice tests. Watch me do these three and stop me when I go wrong."
- "Check this paragraph from my essay for comma splices."
- "Quiz me on however and therefore punctuation until I get five right in a row."

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