Answer:
Correct answer is C . The Russian people were suffering because of World War I and wanted to end the war.
Explanation:
A is not correct because United States didn't interfere, especially not on the side of Bolsheviks.
B is not correct as Russians were against the war practically since the beginning.
C is correct because people opposed the war, were protesting, even started the revolution.
D is not correct as tsar was overthrown in February Revolution. Bolsheviks opposed his authority.