Why was the north against secession of the south

Many maintain that the primary cause of the war was the Southern states' desire to preserve the institution of slavery. Others minimize slavery and point to other factors, such as taxation or the principle of States' Rights. ... All four states strongly defend slavery while making varying claims related to states' rights.

Explanation:

In 2011, at the outset of the sesquicentennial, a Pew Research Center poll found that Americans were significantly divided on the issue, with 48% saying the war was "mainly about states' rights," 38% saying the war was "mainly about slavery," with the remainder answering "both equally" or "neither/don't know."

Explanation:

i think the answer is b.