President James Buchanan Declined to Use Force to Keep the Seven

President James Buchanan declined to use force to keep the seven southern secessionist states in the Union for all of the following reasons except   

A) northern public opinion would not support it.
B) the army was needed to control Indians in the West.
C) he believed that the Constitution required Congressional approval of the use of force.
D) a slim chance of reconciliation remained.
E) he was surrounded by prosouthern advisers who had advised him not use military force against the southern states threatening to secede from the Union.