What weapons led to the creation of a "no man's land" between the trenches?

The correct answer is C) machine gun.

The weapons that led to the creation of a "no man's land" between the trenches were the machine guns.

Although machine guns were used in the United States Civil War, during World War 1 were enhanced and these new machine guns could shoot many more rounds of ammunition a minute. This represented a great advancement in weaponry. This changed the war strategy in the trenches as the firsts lines of soldiers were immediately killed.

The other options of the question were A) airplane, B) tank, and D) poison gas.

where is the subject? hahahaha