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?