You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

what is the first event mentioned?, Context: The Russian Revolution is the series of revolutions in Russia in 1917, which destroyed the Tsarist autocracy and led to the creation of the Soviet Union. Following the abdication of Nicholas II of Russia, the Russian Provisional Government was established. In October 1917, a red faction revolution occurred in which the Red Guard, armed groups of workers and deserting soldiers directed by the Bolshevik Party, seized control of Saint Petersburg (then known as Petrograd) and began an immediate armed takeover of cities and villages throughout the former Russian Empire.
Solution: Russian Revolution
Why? This is a good example, and the Russian Revolution is the first event mentioned.

New input: Which of the following is not a river: Yangtze, Vietnam, or Zhe?, Context: Zhejiang, as the heartland of the Jiangnan (Yangtze River Delta), remained the wealthiest area during the Six Dynasties (220 or 222589), Sui, and Tang. After being incorporated into the Sui dynasty, its economic richness was used for the Sui dynasty's ambitions to expand north and south, particularly into Korea and Vietnam. The plan led the Sui dynasty to restore and expand the network which became the Grand Canal of China. The Canal regularly transported grains and resources from Zhejiang, through its metropolitan center Hangzhou (and its hinterland along both the Zhe River and the shores of Hangzhou Bay), and from Suzhou, and thence to the North China Plain. The debacle of the Korean war led to Sui's overthrow by the Tang, who then presided over a centuries-long golden age for the country. Zhejiang was an important economic center of the empire's Jiangnan East Circuit and was considered particularly prosperous. Throughout the Tang dynasty, The Grand Canal had remained effective, transporting grains and material resources to North China plain and metropolitan centers of the empire. As the Tang Dynasty disintegrated, Zhejiang constituted most of the territory of the regional kingdom of Wuyue.
Solution:
Vietnam