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
I believe D I have read about them but I don't quite remember
Their readers can refer to other articles, or it can back up proof that they aren’t committing plagiarism.
