Because it would be easier to pass without the southern states before they would be restored to the union.
It's caused by the weight of atmosphere pushing down on itself and on the surface below it
I think that it’s A and D because it makes the most since if you think about it because it’s back in the day where they didn’t have much opportunity’s.
U-boats were military submarines used by the Germans. While they were useful against warships, U-boats were the most effective in economic warfare by blockading coasts so resources could not be shipped to Germany's allies. WWI was the first major war that employed submarines in warfare.
Please mark brainliest if this helped :)