Mark Twain wrote The Adventures of Huckleberry Finn in the late 1800s to illustrate Southern culture A. before the Civil War. B. before the Revolution. C. during Reconstruction. D. during the Gilded Age.

The correct option is option A.

Explanation:

The Adventures of Huckleberry Finn are set in Southern antebellum society. The Southern antebellum society was a period in the history of the Southern United States from the late 18th century until the start of the American Civil War in 1861. This period in the South's history was marked by the economic growth of the region, largely due to its heavy reliance on slavery, and of its political influence on the U.S. federal government.

So the correct option is option A before the civil war.