What helped to make the First World War such a long and deadly war? large land areas that troops had to travel over

spy satellites and wireless communication

inventions like the airplane and the machine gun

alliances between Spain, the United States, and Canada

How does the supremacy clause of the u.s. constitution affect the states? o a. it requires each state to establish a supreme court. b. it declares that the federal government can take away state powers if necessary. o c. it allows state governments to overthrow the federal government if necessary. o d. it ensures that the u.s. constitution overrules each state constitution