Through the influence of two byzantine missionary brothers, russia adopted which alphabet?

The two Byzantine missionary brothers St. Cyril and St. Methodius influenced Russia to adopt a script or writing system which came to be known as Cyrillic alphabet. The Cyrillic alphabet owes its origin to Greek alphabet and is closely based on the same, with more than a dozen additional letters invented to represent local Slavic sounds. The script developed in 9th century AD and later it was simplified and regularized. It became the official alphabet of most languages of Eurasian countries and we see in 2007 AD the European Union adopt it as 3rd official alphabet after Latin and Greek.