Answer:
A
Step-by-step explanation:
Well we can start by crossing out "C" and "D" because the act only upheld slavery so either answer would not make sense. I'm sure one could argue this act was significant to the Civil War, but it was not the sole cause, so we can cross out "B." "A" makes the most sense, and is true, as we can see exemplified within The Fugitive Slave Act of 1850.