Which of the following led some people in both the north and south to oppose the abolition of slavery

In the north, people tended to oppose slavery because the north wasn't as agricultural focused like the south. In the south, slaves were needed to tend crops. Still, some people in the north supported slavery for many different reasons. Some northern immigrants were originally people from the south, or people from the south whose slaves had ran away. People were paid to find slaves in the north and bring them back to the south. Even though the north and south and completely different ideas, there were Americans within who didn't agree with those beliefs.

Ithink the answer is d.