Final answer:
The sentence in question is an example of a comma splice, which can be revised by adding a coordinating conjunction or creating two separate sentences. The correct answer is option b.
Step-by-step explanation:
The sentence 'This test is easy, however, I still failed it.' is an example of a comma splice, not a run-on sentence. A comma splice occurs when two independent clauses are incorrectly joined by a comma without the proper conjunction. To correct the comma splice in the sentence, we can add a coordinating conjunction or use a period to make two separate sentences. For example, a revision could be 'This test is easy, but I still failed it.' or 'This test is easy. However, I still failed it.'