Read this sentence:
A disruption of the Federal Union, heretofore only menaced, is now formidably attempted.

What is meant by "a disruption of the Federal Union" in this sentence?

O.A. an interruption in the arguments between the North and the South
O.B. an attempt by the southern states to form their own government
O.C. secession, or the breaking away of southern states from the Union
O.D. a joining of the of northern states with the states that had seceded