After World War I Russia suffered from food and gas shortage, economic crisis and countless deaths of its population. Also, at this time Russia's monarchy was supported by most of the population, which led to the famous February Revolution in 1917. The Revolution ended when the workers' demands were accepted by the new authorities and the last royal family (the Romanov) was sentenced to death. Thus, the right answer is option D. Russia underwent a political revolution in addition to losing citizens during the fighting.