Which of the following statements about run-on sentences is true?

Run-on sentences are indeed a concern when it comes to clarity in writing. A run-on sentence occurs when two or more independent clauses are improperly joined without appropriate punctuation or conjunctions. This lack of proper separation can lead to confusion for readers, as they may struggle to decipher where one thought ends and another begins. Consequently, run-on sentences disrupt the flow and understanding of the text, resulting in decreased clarity. Therefore, saying that run-on sentences affect clarity accurately reflects a key characteristic of this grammatical issue.

The other statements do not align with the definition of run-on sentences. They are not grammatically correct, as proper grammar requires appropriate punctuation or conjunctions between independent clauses. Additionally, rather than making writing clearer, run-on sentences tend to obscure the intended message. Lastly, run-on sentences contain at least two independent clauses, so the assertion that they contain no independent clauses is inaccurate. Hence, identifying that run-on sentences affect clarity captures the essential problem they pose in effective communication.