Abraham Lincoln caused four states to join the Confederacy by

a.

declaring war.

c.

emancipating the enslaved people.

b.

firing on Fort Sumter.

d.

calling for troops.

The correct answer is D. calling for troops.

Abraham Lincoln obviously wanted the states to unite in a confederacy, but not all of them shared his opinion. However, when he threatened he would call for troops in those states, they (Virginia, Arkansas, Tennessee, and North Caroline) joined in.