Answer:
B. Atomic Weapons
Explanation:
Tanks were used near the end of WW1, with tanks such as the Renault FT, Mark 5, and the German A7Vs. Atomic weapons weren't even a concept back then. Gas was used since 1915, invented by a German scientist trying to develop a pesticide, and Machine guns such as the Vickers or MG08 were common in the trenches.
The alliance system was made up of two groups, the Central powers (Germany, Austria- Hungary, Italy(1914), and Turkey). The second group was the Allied powers (Russia, France, Great Britain, and United states).
The Encounter occurred as a result of European <span>explorers crossing the Atlantic Ocean, which famously introduced Europeans to the New World in the west. </span>
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Francisco Vázquez de Coronado</span>