Question

Which statement describes a major reason that america entered World War 1 on the allied side

A.Germany made a secret offer to Mexico to form an alliance to fight the United States.    
B.

France promised to turn over its colonial territories to the United States in return for aid.    
C. President Wilson thought a declaration of war would help the struggling U.S. economy.  
 D. American citizens in Germany were being severely mistreated by the German government.

Answer 1

The alliance with Mexico, however an even bigger reason is when German U boats sank the Lusitania which had on board several US citizens.

Answer 2

A - Germany made a secret offer to Mexico to form an alliance to fight the United States.

This greatly enraged at the time neutral US. For that reason (and also for a couple of other reasons) the United States decided they would declare war on Germany and enter the Great War, as it was called at the time.