Answer:
b. The US brought fresh troops and supplies to the Allies
Step-by-step explanation:
During World War II which had started in 1914, the United States decided to move away from its neutrality position and joined the Allied Power.
During this period, the war has weighed both sides down, but new entrants in the Allied group which is the US, brought more resources both in terms of manpower and weapons to fight and eventually conquer the Central Power.