12.1

4.Why did president Wilson ask congress to declare war in Germany in 1917 despite his earlier efforts to keep the United States out of world war 1?

B. He was concerned about the German aggression outlined in the Zimmerman note.

1.How did the use of machine guns change the nature of warefare durung world war 1 ?

B. It gave a tactical advantage to defensive forces.

5.Which factor caused the rapid escalation of world war 1?

B. The elaborate system of alliance between European nations

2.What affect did Germany's unrestricted submarine warfare against Britain have on the balance of power in world war 1?

C. The United States entered the conflict, siding with the allied powers against Germany.

3.How did trench warfare affect soldiers during the world war 1?

D. It led to higher casualties and poor conditions for soldiers.