C. The United States had been formed by a voluntary joining of
states.
Explanation:
The Confederate States of America was formed by 11 states that seceded from the Union in 1860-1861, following the election of abolitionist Abraham Lincoln as president of the United States. They adopted the US Constitution with some changes that guaranteed slavery. The southern economy was mainly agricultural and needed much slave workforce. States rights were given a higher constitutional rank and the central government could not levy protective tariffs and direct capitation taxes; this limited its capacity to wage war and get revenues.
