Part 1
An aid is that countries just help each other out like giving food or water when there is a shortage. A treaty is a formal agrement between countries. and a treaty is the closest frendship countries can have they would go to war for each other.
Part 2
They are not on the diagram because the diagram is before U.S. joined WWI.
The U.S. joined WWI in 1917 when they allied with France, Russia, and Britain.
The U.S. joined WWI in 1917 when they allied with France, Russia, and Britain.