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
Henry David Thoreau opposed the Mexican War, so you could consider him an opponent of Manifest Destiny. Manifest Destiny was an overarching idea or concept, but it's practical application took place in many different events and contexts.
HOPE THIS HELPED!!
A. Primary Sources are raw materials of time, original documents created at that time.
