Read this passage: Russia's leader Czar Alexander II tried to modernize Russian society in the late 19th century. One of his major accomplishments was ending serfdom, a forced-labor system similar to slavery. However, Alexander II was assassinated in 1881, and the czars that followed him reversed many of his reforms. These leaders were so harsh that a group of revolutionaries called the Bolsheviks eventually rebelled against them and overthrew the Russian government in 1917. Which statement best describes the main idea of the passage? O A. The system of Russian serfdom was a forced-labor structure that was similar to slavery. B. Efforts to modernize Russia in the 19th cent Sailed to protect the country from a revolution. O C. Russian leaders were called czars until the Russian government was overthrown in 1917. O D. Czar Alexander II was responsible for the rise of the Bolshevik rebel group in Russia.