which of the following statements about World War 1 would be most difficult to prove and disprove

Question

a. American casualties were more numerous than in any other war.
b. it was the first war in which the opposing sides used airplanes
c. the U.S government spent more on armaments in 1917 than during any other year
d. it was the first war in which American forces fought on foreign soil.
e. the war strengthened democracy in the united states

Answer 1

Right.

Answer 2

it will be 1

Answer 3

E is right? Me. Sue

Answer 4

Yea