Which is an example of a run-on sentence?

• A. The patient arrived early, she was tired.
• B. The patient arrived early; she was tired.
• C. The patient arrived early she was tired.
• D. The patient arrived early, and she was tired.

Answer: (C)

A run-on happens when two complete thoughts are joined without proper punctuation or a linking word. Here, two independent clauses—“The patient arrived early” and “she was tired”—could each stand as a sentence. When they’re placed together without any punctuation or conjunction, you get a fused sentence, which is a type of run-on.

The version with just a comma between the two clauses is a comma splice—that’s another common run-on form. The version with a semicolon correctly links the two independent clauses. The version with a comma plus a coordinating conjunction is a properly formed compound sentence. The version with no punctuation between the two independent clauses is the fused sentence, the run-on shown in this item.