Which best describes nullification?

C. the idea that a state could refuse to follow a federal law it disagreed with

Explanation:

Nullification is a legal capability states have to disagree with federals laws if one of many states consider such laws are unconstitutional. This is in theory,  but in practice this creates conflict because federal courts and many states courts consider the federal laws ultimate interpretation cannot relay on states as there are also legal statements which support the supremasive of federal goverment for this matter ( Supremacy Clause of  the Constitution and Article III of the Constitution).

b)

it created free trade throughout the colonial territories.

i think it would be a