<span>The correct answer is C. Swimming is great cardiovascular exercise.
In this sentence, "swimming" is a gerund. It functions as the subject of the sentence. In the first option, "swimming" is part of the verb phrase ("were swimming"). In the second option, "swimming" is part of the adjective and describes the team. Only in the final sentence does "swimming" function as a noun, or a gerund.</span>
You didn't list a book, paragraph, passage, not even a sentence or source.. how are people supposed to answer this?
A frame narrative is like a fake story so the answer is C