SAT® · Reading and Writing: Boundaries — Between Sentences
The Period, the Question Mark, and the Exclamation Point
A period, question mark, or exclamation point ends one complete sentence before the next begins. On the test, the period is almost always the right choice because the surrounding clauses are statements, not real questions or exclamations.
Two independent clauses, each with its own subject and verb, cannot sit in the same sentence without something connecting them properly. An end mark is the cleanest fix: it closes the first clause completely and lets the second start fresh as its own sentence. The period does this job constantly because most sentences in formal writing are statements. Question marks and exclamation points only work if the clause they close is actually a direct question or an actual exclamation, written as one.
Work through 'The results surprised the team they repeated the experiment.' Read it clause by clause: 'The results surprised the team' stands alone, and 'they repeated the experiment' stands alone too. Jammed together with no punctuation, that's a run-on. Put a period after 'team' and capitalize 'They,' and both clauses become legal sentences. A comma alone would create a splice, since a comma can't join two independent clauses by itself.
The trap question marks exploit is the reported question: 'The researchers asked why the ice melted so fast.' It sounds like a question because the word 'why' shows up, but the sentence as a whole is a statement reporting that an inquiry happened. Nobody is asking anything out loud in that sentence, so it gets a period. This topic sits next to comma splices and run-ons in the same family of boundary errors: all three ask whether the clause on each side of the punctuation can survive alone, and the end mark is the most common cure when no connecting word is available.
Key terms
- Independent clause
- A group of words with a subject and verb that can stand alone as a complete sentence.
- Run-on sentence
- Two independent clauses fused together with no punctuation or connecting word between them.
- Comma splice
- Two independent clauses joined by only a comma, which is not strong enough to connect them.
- Reported question
- A sentence that states someone asked something, rather than asking it directly, so it ends with a period.
Watch it explained
- How it worksHow does a period turn two fused clauses into two structures that each stand up alone?
- Worked exampleWalk me through punctuating 'The results surprised the team they repeated the experiment' with an end mark.
- Common mistakeWhy isn't a question mark right in 'The researchers asked why the ice melted so fast' when a question is reported?
Check yourself
End of topic.