Answer:
Because of the Alliance with Serbia, France and Britain, and fear of German expected demands
Step-by-step explanation:
The reason the Russian provisional government keeps Russian troops involved in World War I after the Russian revolution of 1917 is because of the "of the Alliance with Serbia, France, and Britain."
During this period, Russia still relies heavily on the loans they are getting from Britain and France, and at the same time, they also want to maintain the alliance with Serbia.
The Russian government also feared the kind of demands the German will ask of them if the Germans win the war.