The corrects answers are A) machine guns, B) cannons, and C) tanks.
The weapons that helped to create a stalemate on the Western front were machine guns, cannons, and tanks.
In terms of war, we understand a "stalemate" when the battle is so tough and disputed that there is not a clear advantage or victory to neither side. The weapons in World War 1 that helped to create a stalemate on the Western front were machine guns, cannons, and tanks.
In the West front of World War 1, there were situations such as the French couldn't defeat the Germans completely at the battle of the Marne or that defending a position became so complicated, that helped to create a stalemate in the conflict.