ответь те на вопросы , буду . when did russia stop being a monarchy and become the republic? where are the altai and the caucus mountains situated? what other russian mountain chains do you know? where are the rivers lena and ob situated? what do you think are the most important events in the history of russia?

Russian stooped being a monarchy and became a republic after Russian Revolution in 1917.
The Altai and the Caucus mountains are situated in Russia. 
There is another mountain chain in Russia called Ural mountains.
The rivers Lena and Ob are situated in the Asian Russian part.
The most important events in the Russian history are: World War II and the Russian Revolution.