What you are reading and think what is in the text so you can understand it better.
C. it was able to use military bases in allied territories i think
Well, they both are to blame that's a fact. Although I do tilt slightly more to the fact that the Britains were the ones who should take the most blame. The British made the colonists land at that time attempted.
Because the south in large part were built on slaves. They didn't have factories or anything like the north did. They had cotton and assorted vegetables. In large part many will say that is also what lost them the war.
My answer is The Union was able to stop Confederate supplies from entering Florida.