The North won the Civil War because

A. they had superior numbers of military forces
B. the South’s principle of States’ Rights sometimes prevented them for working together successfully
C. the North’s naval blockade prevented the South from selling much of its agricultural produce, which brought widespread financial ruin
D. President Lincoln accepted the offer of war elephants from the King of Siam
E.the rebel yell intimidated Union soldiers
F. of massive numbers of black recruits in the Confederate Army
G.A, B, and C only H. D, E, and F only

I would say G, am I right?

I agree.

Btw -- I like D -- <g>