In this paper we characterize the exceptional theta lifting from Ga to C-3
by means of the existence of the simple pole at s = 1 of the spin L-functio
n for GSp(3) and by means of the nonvanishing of certain period on GSp(3) A
mong other results, we also prove the lifting from G(2) to C-3 is functoria
l at local unramified places.