A. A state had the right to choose not to follow a law it thought was
unconstitutional.
Step-by-step explanation:
South Carolina's basic argument for nullification was that a state had the right to choose not to follow a law it thought was unconstitutional.
The Nullification Crisis occurred because of tariffs. A tariff is essentially a tax on foreign products. The North favored tariffs because it helped make people in the United States buy from their businesses instead of foreign ones. The South despised tariffs because it made their goods less favorable to foreign countries, plus now if they were to buy goods from overseas, it would be more expensive.
South Carolina declared that the tariffs were "null and void" and that they would not be following them any longer. They believed that it was unconstitutional and did not have to follow it if they did not wish to. This raised tensions between the state government and the federal government and threatened the balance of power between the two.