Answer:
A prolonged war and greatly increased the number of casualties in the war
Explanation:
In World War I we saw the introduction of chemical weapons, machine guns, artillery, and tanks. All of this resulted in trench warfare and the lack of tactics to fight the new weapons meant that the war would be longer and a lot deadlier than it would have been without those weapons. It dragged for years from one stalemate to another and claimed a lot of lives.
#1 would be either d or b I narrowed it down.
#2 would be c or the other answer it might be b from there chose and use notes !!
