Question

All of the following were new techniques of warfare in World War I EXCEPT?
A) machine guns
B) tanks
C) battleships
D) poison gas

Answer 1

No proper answer. The Gatling gun appeared decades before WW I as did battleships.

Answer 2

so what is it?

Answer 3

If you mean what answer does your teacher want you to give, then it's most likely battleships, since they were clearly in existence before the war.