(a) why didn’t the united states enter the war earlier?
(b) what events pushed the united states to enter the war?
(c) why did the united states enter on the side of the allies?

A. In 1917, Germany, determined to win its war of attrition against the Allies, announced the resumption of unrestricted warfare in war-zone waters. Three days later, the United States broke diplomatic relations with Germany, and just hours after that the American liner Housatonic was sunk by a German U-boat.

B. The primary events that led to the United States declaration of war against Germany were the Zimmerman Telegram and Germany's announced intention to resume unrestricted submarine warfare.

C.The United States entered the war because of the Germans' decision to resume the policy of unrestricted submarine warfare, and the so-called "Zimmerman telegram," intercepted by the British, in which Germany floated the idea of an alliance with Mexico. ... They abandoned it in the face of US pressure earlier in the war.

what do you                                                                                                                                              

the graph shows the spread of railways in the 1800s.

based on the graph, the conclusion that can be drawn about germany is answer d)   by 1880, germany had more rail lines than great britain and russia.