What is the main currency used for trade in WOW?

Gold, Silver and Copper
Rubies
Dragon skins
Mana points

Info: Any item can be bought with gold, silver or copper. The main currency for buying and selling goods is gold. To get one golden coin, a player has to collect 100 silver coins. 1 silver coin is equivalent to 100 copper coins. The game also allows exchanging items between players.

About this trivia

Trivia about "World of Warcraft" game, sometimes also called WoW, is a global multiplayer online role-playing game (MMORPG) developed by Blizzard Entertainment, which gave life to the Warcraft universe. In 2008, World of Warcraft counted more than 11.5 million subscribers and to this day is included into the Guinness Book of Records as the world's most popular and largest MMORPG.