Answer:
Slavery played the central role during the American Civil War. The primary catalyst for secession was slavery, especially Southern political leaders' resistance to attempts by Northern antislavery political forces to block the expansion of slavery into the western territories.
The American colonists greatly benefited from having allies during the American Revolution. One of America's most prominent allies was France. France sent over supplies, troops, money, and individuals like Marquis De Lafayette to help the colonists. Lafayette played a critical role in America's success, as he helped the colonists to develop battle strategies along with general organization skills. The colonists also received help from Prussian General Baron Von Steuben. Stueben tought the colonists how to use bayonets at the end of their guns and helped to create sanitary conditions in colonial camps.
Comparative advantage I would think. Yep, Google-sensei confirmed it:) Comparative advantage is the answer.
The correct answer is c : Passed laws
