Why was Missouri's application for statehood so controversial?

A. Missouri was very poor, and the other states knew that if it was added to the Union, a large percentage of their federal tax dollars would go toward improving Missouri's infrastructure.
B. Missouri added a clause to its application allowing it to leave the Union if it ever wanted to become a separate nation.
C. Missouri wanted to be added to the Union as a slave state during a time when the slave-state-to-free-state ratio was even. Therefore, Missouri's admission would cause an imbalance in power in the U.S. Congress.
D. Missouri agreed to apply for statehood, but only on the condition that it would never have to pay federal taxes.