The main idea of nullification was that
the president could enact any law that he
the supreme court could overturn presidential decisions
congress had power over the supreme court
states could override federal laws

The correct answer is states could override federal laws.

Nullification is the idea that states have the ability to override federal laws if they believe that the law in question is unconstitutional. This idea has never been supported by the US courts but has been used several different times to justify state actions. This includes the Virginia and Kentucky Resolution that was developed during the presidency of John Adams. This idea was also used in the Nullification Crisis in the 1820's by the state of South Carolina.