Answer:
D. It gave the southern states a justification for secession.
Step-by-step explanation:
Let's talk about each option.
A. It decided the question of slavery based on popular sovereignty.
Yes. This concept estabilished that each territory decided on it's slavery legislation;
B. The president was elected with only 40% of the popular vote.
Yes. Lincoln had 39.8% of votes.
C. The nation was primed for a civil war.
Yes. There was the civil war from 1862 to 1865.
D. It gave the southern states a justification for secession.
By elimination, this is false, and the answer to this question.