I am pretty sure that the answer is D correct me if I'm wrong hope this helps.
Answer:
the cause of WW1 was because russia began due to its alliance with serbia germany declared war on russia.
Explanation:
Well without full context I would assume Trench Warfare because thats what 3 1/2 of the 4 year wars where full of.
Due to trench warfare the machine gun caused stalemates because it was difficult to move up
known as the Congo Conference or West Africa Conference, regulated European colonization and trade in Africa during the New Imperialism period and coincided with Germany's sudden emergence as an imperial power.
