All of the following were main causes of World War I except

1. the Russian Revolution.

2. Imperialism.

3. the building of large armies.

4. Nationalism.

The correct answer is 1. The Russian Revolution

Explanation:

The four main causes of the first World War were, MAIN

i. e. Militarism, Alliances, Imperialism and Nationalism.

The Russian revolution had no part to play in the cause of the first World War.

In fact, World War I started in 1914 while the Russian revolution only took place in 1917, closer to when the war was about to end anyway. The revolution was against the ruler of the Tsar and his family, mostly led by local peasant revolts.