In every document or essay, the thesis is a clear, concise statement of an author's primary point of view or main argument. Of the choices below, which most accurately reflects this source's central thesis statement?

a. Slavery was confined to just a few people in the early days of the nation until the rise of the cotton plantation in the South.
b. The Founding Fathers put in place a road map for gradual emancipation that was later undermined by the importance of slavery to the Southern economy.
c. By the late eighteenth century, American slaves were performing a range of tasks throughout the colonies, but succeeded in finding liberty only in northern states.
d. By the late eighteenth century, most northern states enlisted laws providing ex-slaves with equal rights, and the institution of slavery had become confined to the South.