context: The Prioksko-Terrasny State Natural Biosphere Reserve named after Mikhail Zablotsky is a specially protected natural territory of the Russian Federation. Located on the left bank of Oka, in Serpukhov district of Moscow region. The reserve covers an area of ​​4945 hectares, being one of the smallest conservation areas in Russia. This is the only state nature reserve in the Moscow region.
question: On the banks of which river is the Prioksko-Terrasny state natural biosphere reserve named after Mikhail Zablotsky?
answers.text: Oka