what was the main cause of the russian revolution?

Yes C.

To the answer above me, communism didn't usher in any prosperity, it only took money from people and gave it to others. In fact it delayed prosperity for 70 years from which Russia still suffers today.

C: Mainly the poverty/starvation of the Russian people caused partly from the expence caused by the war...partly harsh environment.People had had enough! there was an uprising of the peasants against the crown for a fairer deal, it was'nt forthcoming so they killed off the throne..then who to rule? communism born..and with that some prosperity which lasted 80 years.

C: The tremendos war losses of World War I.

All the above were factors, but the will of the people to stop living as serfs was the deciding factor.