Question

the secession of south carolina from the union in 1860 was prompted by
a the election of abraham lincoln as president.
b the threat of the congress to abolish slavery.
c refusal of congress to pass the fugitive slave law.
d the invasion of south carolina by union forces at ft. sumter.
e the confederate success at the battle of bull run (manassas).

Explanation:

South Carolina seceded in December 1860, right after Abraham Lincoln's presidential election. Lincoln's anti-expansion of slavery stance alarmed the pro-slavery state, as they feared he would undermine slavery. The other options are incorrect: Congress did not threaten immediate abolition in 1860, the Fugitive Slave Law was already passed earlier, the Ft. Sumter conflict happened after secession, and the Battle of Bull Run was in 1861, well after secession.

Answer:

A. the election of Abraham Lincoln as President.