Which of the following statements best compares the use of chemical weapons and machine guns in world war i?

both chemical weapons and machine guns to advance the battles on the western front.
both chemical weapons and machine guns to create a stalemate on the western front.
neither chemical weapons nor machine guns were used by the allies on the western front.
neither chemical weapons nor machine guns were used by the axis armies on the western front

I believe the answer is: Both chemical weapons and machine guns helped to create a stalemate on the Western Front.

At that time, Allies almost won the battle on the Western front, until the German millitary started to use chemical weapons such as phosgene, chlorine, and mustard gas. Combined with a more advanced machine guns, the German army managed to save themselves from defeat and bring the battle into a stalemate.

for this case we have the following equation:

we apply distributive property to the terms within parentheses.

subtracting 2 on both sides of the equation: