Fused sentences are run-on sentences. it has at least two parts either one of which is an independent clause, but the two clauses have been fused instead of being properly connected. When these clauses are joined by only a comma, it is a run-on sentence called the comma-splice.
The choices above, a,b, and d are examples of comma splices. When you use a comma to join or connect two clauses that can stand by themselves, it must be accompanied by a conjuction like but, and, for, so, yet, or, nor.
Therefore, the answer is letter c. The sentence in letter c does not constitute a run-on sentence.
