Answer:
C. Trench warfare
Explanation:
A's incorrect as alliances have existed for thousands of years
B's incorrect as an infantry charge's greatest weakness is the machine gun for obvious reasons
D's incorrect as both sides had machine guns, and was not the reason for victory.
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This leaves C, which makes sense as troops would be forced to hide on lower ground due to the deadliness of machine guns
Generally speaking, popular sovereignty means that the people of a state or country are ultimately in control over their government--usually by electing representatives to craft legislation on their behalf.
It caused instability on government and economies worldwide,as the destruction caused by wwi has caused unrest among nations,many also suffers great economic dilemma due to destruction on infrastructures (e.g. factories, hospitals),also due to the lack of labour caused by death and injuries. Some nations also closed trading to secure their own economic development. The governments faced instability due to unrest caused by hyperinflation and unemployment
