I have tried three times but my answers don't post. Try this one.
OK, we'll try again. There are more acid/base theories than we can shake a stick at but the simplest is that acids provide hydrogen ions (H^+) in solution and bases provide hydroxyl ions (OH^-) in solution. That means bases contain O and H. Two other popular theories are the Bronsted-Lowry acid/base theory and the Lewis acid/base theory.