Even if passed by two-thirds of both houses of congress a constitutional amendment still must be

hello!

according to the passage the most suitable options are two. the first one is "by leading the aef to victory in several key battles" like the battle of saint- mihiel and the battle of cantigny mentioned in the passage you copied here. the second one is "by the aef and allied forces defeat germany" since the passage says that his army destroy the german resistance in the meuse- argonne offensive. and also, "by insisting that the aef operate as an independent force".

hope this

the answer is a) high entry costs