What is the genre of World of Warcraft?

MMORPG - Massively Multiplayer Role-Playing Online Game
RTS - Real Time Strategy
Casual
Collectible Card Game

Info: Massively multiplayer online role-playing game or MMORPG is a computer game in which the two genres of role-playing games and mass online games are combined in one. The main feature of the genre is the interaction between a large number of players within the virtual world.