(A) ** Grenades
(B) Tanks
(C) Airplanes
(D) Flamethrowers
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: -Hand grenades were nothing new at the start of World War I. Small hand-thrown explosive bombs date back to the 8th century, when Byzantine soldiers packed Greek fire into ceramic vessels, and to 10th century China, when gunpowder charges were loaded into fused clay containers.
Concept note-3: -World War I popularized the use of the machine gun-capable of bringing down row after row of soldiers from a distance on the battlefield. This weapon, along with barbed wire and mines, made movement across open land both difficult and dangerous. Thus trench warfare was born.
Concept note-4: -The main ones utilized were the American Mark I, French VB rifle grenade with discharger, French Model 1916 Smoke and suffocating grenade, British Type No. 27 combination hand and rifle grenade (white phosphorus), French Model 1916 Lachrymatory and Irritating Grenade and French Model 1916 incendiary grenade.