What nations experienced major revolutions in the twentieth century?
- russia
- france
- japan
- china

I would say Russia or China, but Russia is probably the best answer because of the political importance of the Bolshevik Revolution and the changing effect of Russia such as shown with the Berlin Wall, World Wars, etc.

Russia and China

The Russian Revolution, 1917 led by Lenin and the Communist Party overthrows the monarchical rule of the Tzars and creates a socialist model where the influence spreads to Eastern Europe and other regions of the world formating a socialist world with its own rules.

The Chinese Revolution, 1949 is led by Mao Zedong, who embraces a particular form of communism after winning the civil war initiated back in 1927. It resulted in the affirmation of China in world politics and departed from the URSS shortly after the Chinese Communist Party settles.

Both revolutions shape a geopolitical sphere among them we can point out:

Differences:

Russia (USSR) recognized Mongolia which China saw as part of its territory

China opposed industries with Soviet and Chinese funds (mixed investments)

The scientifical and technical aid given to China by the USSR suspended in 1958

Similarities:

Both had "cult of the personality" (Lenin, Mao)

They originated in the context of agricultural and non-industrial economies

They gave an end to well-established traditions of rule by birth: The Czars, the Chinese Emperors