Can you add burning crusade to a trial account

No, I think you need to buy the whole game,. Be careful, WoW is very good, and so addictive, but the downloading of updates and patches take a LONG time, 6-8 hours, and you have to do these BEFORE you can play, so worth it though. Also, I would recommend purchasing Wrath of The Lich King, but make sure you install Burning Crusade FIRST, then Wrath of the Lich King