I believe the answer is C. Everyone in the north believe slavery was wrong and everyone in the north did not.
Eventhough it may not be every single one, this option best shown the amount to answer 'how many' viewed slavery.
The southern believed that there is nothing wrong because they got used to it to the point it became norms for them. The northern on the other hand, believed that slavery was wrong and plantation ownees should rely on technological advancement for the labor isntead.