Final answer:
Russia transitioned from a czarist regime due to sociopolitical and economic turmoil and the Bolshevik Revolution led by Lenin, which promised radical changes like peace, land, and bread, eventually leading to the establishment of a communist state.
Step-by-step explanation:
Russia moved away from a czarist regime in the early twentieth century due to a combination of sociopolitical and economic factors, including the failure of Czar Nicholas II to address Russia's deep-seated internal problems, the military defeats and high casualties of World War I, and the rise of revolutionary ideologies that culminated in the Russian Revolution of 1917.
The correct answer to why this shift occurred is B) Lenin led the Bolsheviks to revolt against the czar. This movement was further propelled by widespread discontent, which accelerated with Russia's continued struggle in World War I, leading to the abdication of the czar and the eventual rise of the Bolsheviks, who promised peace, land, and bread to the war-weary Russian populace.
Not long after, they began establishing a communist state, after winning the civil war against varied opposition groups collectively referred to as the 'White Army'.