Answer:
C. Before the Civil War.
Explanation:
Based on the root word of the affix "ante-", it is easy to say that any word that comes with this word will mean "before" or preceding it. Likewise, the root word "belli" means "war" or "fighting". Therefore, if these two words are put together, then the new word is likely to refer to the period before a war.
Now, the word "Antebellum" is a period in American history that is usually used by the Southern states to refer to the period or time before the Civil War. Therefore, the correct answer is option C.