Final answer:
The word or phrase that best completes the statement about Europe at the end of World War I is surrender, Austria-Hungary, genocide, war guilt clause (option a).
Step-by-step explanation:
The word or phrase that best completes the statement about Europe at the end of World War I is surrender, Austria-Hungary, genocide, war guilt clause (option a).
At the end of World War I, Austria-Hungary surrendered, leading to the breakup of the empire. The war guilt clause was included in the Treaty of Versailles, which forced Germany to accept full responsibility for the war. However, genocide was not directly linked to the end of World War I.