Answer:
Option: A. Missouri wanted to enter as a slave state, which would upset the balance of power between slave and free states in the Senate.
Explanation:
Missouri wanted to enter as a slave state which created tension among the free states. The congress had the right to pass free or slave status of any state formed from the territories. The slave states admitted that states should have the same benefits as others, and be able to decide for themselves if they wanted to support slavery or not. The free states were afraid of slavery becoming permanent while the slave states worried about abolishing slavery.