The code of chivalry was intended to prevent lawlessness on the part of knights.
I would put C, to be honest. so that people can understand just a bit better.
These advances in the history of technology stimulated societies to adopt new ways of living and governance.
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