The correct answer is option 'C' - February Revolution.

The February Revolution in 1917 marked the beginning of the end for Tsar Nicholas II's reign as the last Emperor of Russia. It was a significant event that eventually led to his abdication. Here is an explanation of the events surrounding the February Revolution and its impact on Nicholas II:

1. Background:
- Russia was facing numerous issues that contributed to growing discontent among the population. These included economic hardships, food shortages, the strain of World War I, and the autocratic rule of Nicholas II.
- The Tsar's decision to personally lead the Russian army on the Eastern Front during World War I further distanced him from the domestic affairs of the country, leading to a power vacuum in the capital, Petrograd (formerly St. Petersburg).

2. Petrograd Strikes and Protests:
- In February 1917, strikes and protests erupted in Petrograd due to food shortages and deteriorating living conditions. Workers from various industries, joined by soldiers and other segments of society, took to the streets demanding change and reform.
- The strikes quickly spread, and the protests turned violent, with clashes between the demonstrators and the police and military forces.

3. Formation of the Petrograd Soviet:
- The workers' strikes led to the creation of the Petrograd Soviet, a council representing the interests of workers, soldiers, and other groups. It became a central force in organizing the revolutionary movement.
- The Soviet was initially moderate and sought to cooperate with the Provisional Government, which was formed after the abdication of Nicholas II. However, it gradually gained more influence and became more radical in its demands.

4. Abdication of Nicholas II:
- As the protests and strikes intensified, the military and political elite began losing faith in Nicholas II's ability to govern and maintain order.
- In an attempt to quell the unrest, Nicholas II ordered the military to suppress the demonstrations, but they refused to fire upon the protesters.
- Faced with the loss of support from the military and growing pressure from both the Petrograd Soviet and the political elite, Nicholas II abdicated on March 2, 1917, ending the Romanov dynasty's rule.

In conclusion, the February Revolution of 1917, characterized by strikes, protests, and the formation of the Petrograd Soviet, led to the abdication of Tsar Nicholas II. This event marked a turning point in Russian history, paving the way for the establishment of the Provisional Government and eventually the Bolshevik-led October Revolution later that year.