I am afraid I do not follow: surely water is a compound containing two elements, and air is a mixture of a great many?

Oh, three or four people at the least, I think, only most of them can only control one of the elements: for more than that you would wish perhaps to speak to Korra, whom they call the Avatar. I am given to understand it is a very great sign of power, to control all the elements at once.

[He tilts his head.] But their ability appears to be genetic, after a fashion; is yours genetic as well, or can it be taught?