Why is WWI referred to as the first modern war?

it is considered the 1st modern war because it had bombs, First tanks, first planes, first chemical weapons, and first effective machine guns were used. Also the first war that involved so many nations around the world. They worked in factories that made war goods.

nations must cooperate to bring about and maintain world peace.

nations must not wage wars or commit war crimes in a desire to control other nations.

i think i know which options you have but if these aren't options let me know