(A) ** helicopter
(B) machine gun
(C) poison gas
(D) tanks
EXPLANATIONS BELOW
Concept note-1: -Heavy artillery, machine guns, tanks, motorized transport vehicles, high explosives, chemical weapons, airplanes, field radios and telephones, aerial reconnaissance cameras, and rapidly advancing medical technology and science were just a few of the areas that reshaped twentieth century warfare.
Concept note-2: -The advancement of technology in WWI created a shift toward the mass killing ability in Wars. Machine guns could kill rows of soldiers at once, and gas attacks could kill hundreds of soldiers. The advancement of this technology must be seen as negative.