Which situation was the greatest cause of the events known as the Nullification Crisis?

a
a military draft instituted to fill the need for soldiers during the Mexican War
b
a series of import taxes that were unpopular in one region of the country
c
disagreements over westward expansion and the protection of enslavement
d
disputed election results that led to Andrew Jackson's second term in office

c

disagreements over westward expansion and the protection of enslavement