Aside from supplies, what do these passages suggest that Americans provided the war effort during World War I?

"After two and a half years of war, the Allies were exhausted. The Allies were demoralized. American forces supplied them with much needed supplies and a boost in numbers. The Americans also provided them with something much, much greater than this however..."

"I have never seen or heard of such an elaborate, complete line of defense as the British had built at this point. There was a trench with dugouts every three hundred
yards from the front line in Ypres back four miles to and including Dirty Bucket. Everything was fronted with barbed wire and other entanglements. Artillery was
concealed everywhere. Railroad tracks, narrow and standard gauge, reached from the trenches back into the zone of supply. Nothing had been neglected to hold this line, save only one important thing, enthusiasm among the troops, and that was the purpose of our presence." -Joseph Douglas Lawrence, American WWI Soldier


A. Trenches and dugouts
B. Artillery shells
C. Battle strategy
D. Refreshed soldiers