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SAT Reading and Writing skill page

SAT Sentence Boundaries Practice

Decide where one complete idea ends and another begins so fragments, run-ons, and comma splices stand out.

Practice sentence boundaries in DolphinPractice questions
10-15 min practice time3 questions on pageStandard English Conventions
Practice time10-15 min
Practice questions3 questions
Best forStandard English Conventions

What this tests

What to know for this SAT skill

Dolphin practice questions

Practice your skill

Question 1 of 3Easy
Which choice creates a complete sentence?
  1. Because the storm ended.
  2. The storm ended, and the team resumed practice.
  3. Although the storm ended and the field.
  4. When the storm ended, and.
Show answer and solution
Correct answerB. The storm ended, and the team resumed practice.

Solution walkthrough

  1. This choice contains two complete ideas joined correctly with a comma and "and. "
Question 2 of 3Medium
Which choice fixes the comma splice? The lab opened at nine, the students arrived early.
  1. The lab opened at nine the students arrived early.
  2. The lab opened at nine; the students arrived early.
  3. The lab opened at nine, arrived early.
  4. The lab opened at nine and arriving early.
Show answer and solution
Correct answerB. The lab opened at nine; the students arrived early.

Solution walkthrough

  1. A semicolon can join two closely related independent clauses.
Question 3 of 3Hard
Which choice completes the sentence correctly? The artist revised the mural several times ____ the final version kept the original color scheme.
  1. and
  2. but
  3. , but
  4. ; but
Show answer and solution
Correct answerC. , but

Solution walkthrough

  1. Two independent clauses joined by "but" need a comma before the conjunction.

Avoid these traps

Common mistakes on this skill

Treating a dependent clause as complete

Words like because, although, and when often make a clause dependent.

Using only a comma between complete sentences

A comma alone cannot connect two independent clauses.

Ignoring the conjunction

A coordinating conjunction can join clauses, but punctuation still matters.

Study plan

How to practice this skill in Dolphin

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  1. Mark whether each side of the punctuation can stand alone.
  2. Use a period or semicolon for two complete sentences.
  3. Use comma plus a coordinating conjunction when the logic calls for it.
  4. Reject answer choices that leave a fragment.
Practice sentence boundaries in Dolphin

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FAQ

Questions about SAT Sentence Boundaries Practice

What are sentence boundaries on the SAT?

Sentence boundaries are the rules that separate complete sentences from fragments and run-ons.

Is this different from punctuation practice?

It overlaps with punctuation, but sentence boundaries focus specifically on whether clauses are complete.

How do I spot a run-on quickly?

Look for two complete thoughts pushed together without correct punctuation or a coordinating conjunction.