The correct answer is - The Cyrillic alphabet and Olga's selection of the Byzantine Church.
The Russians saw themselves as Slavic people, so when Kliment and Naum from Ohrid in Macedonia reformed the Glagolic alphabet and turned it to the Cyrillic, and it started to spread around among the Slavic people, it came natural for the Russians to accept it and use it, thus separating them from the countries that were using the Latin alphabet.
Also, Olga's decision to accept the Byzantine Church, instead of the Roman Church, had huge impact on the relations of the Russians with the western part of the continent, thus making them move away from their ideals and perceptions.
