The last event happened in 1917. It is the entry of The united state of America entered into the first world war in 1917. So the correct option is A.
What is the role of America in the first world war?
The first world war broke out in July 1914. In the Initially stage America was the neutral country. While the individuals American were supporting one side and the other side but the majority of people were supporting the allies.
There are many reasons to enter the USA in the first world war are espionage from the central powers, allies' power borrowed more than 2 billion, unrestricted german U-boat warfare, and Zimmerman telegram.
Therefore the correct option is A.
Learn more about the first world war here:
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