Answer:
B. The alphabet
Explanation:
The Russian language is written with the Cyrillic script, which was developed in Medieval Bulgaria based on the Greek script used at the time in the Byzantine Empire. In fact, the name "Cyrillic" comes from the name of a Byzantine monk: Saint Cyrill.
The Cyrillic script is also used in Ukraine, Serbia, Bulgaria, and Belarus.
They mostly grew wheat, barley, oats, rye, and corn. because of this, they were basically known as the "Breadbasket". So I believe your answer would most likely be wheat.