The correct answer is B) slave states feared of losing political power.
Politicians from slave-owning states feared adding non-slave states to the United States because slave states feared of losing political power.
The slave states really were afraid of the idea of the free states gained more power in the House of Representatives and the Senate. Free states had more representants in the House because their population was larger. Then, the slave states were worried that the free states were going to add amendments to eliminate slavery or limit it. Southern states economy depended too much on slavery.