(A) Poison Gas
(B) machine guns
(C) airplanes
(D) ** all of the above
EXPLANATIONS BELOW
Concept note-1: -Military technology of the time included important innovations in machine guns, grenades, and artillery, along with essentially new weapons such as submarines, poison gas, warplanes and tanks.
Concept note-2: -Their use of advanced artillery, mortars, and machine guns turned battlefields into a “no man’s land” where no one could survive. Mortars were especially effective as a firearm due to the destruction they caused.
Concept note-3: -The First World War saw the first widespread use of both fixed-mount and portable mechanical flamethrowers. Reports first appeared in early 1915 after the Germans deployed the weapon against French forces near Verdun.