Which economic advantage did the northern states hold over the southern states by the middle of the 1800s? A. lower labor costs

B. larger crop yields per acre

C. a tighter trade relationship with Europe

D. a better transportation network

There were 2 possible answers. But It could not be B because The Union had a industrial line instead of a Agriculture. So The Answer Is D.

Explanation:

Answer is D

a. favoring native born americans over immigrants.

agree with wilson that weakening the treaty would threaten world peace.