The answer would be C. By using parallel structure, Roosevelt emphasizes the challenge the country faces in transitioning from peacetime to wartime.
The literary device parallelism is employed to emphasize how hard it is prepare for a wartime scenario. Parallelism is used mostly to provide emphasis in many moving passages and is efficient when trying to persuade or convince one's audience.
Example:
It was dark because a new era was upon the nation. It was dark because change was coming. It was dark because the struggle had only begun.
In this example, repeating the phrase "It was dark" places emphasis on the ominous tone of the prompt and allows the reader to feel the gravity of the situation.
