A:K2SO4 = 2K++SO4-2
B:Ba(OH)2 = Ba2++OH2-
C:Fe2(SO4)3 = 2Fe3++3SO42-
D:Mg(NO3)2 = Mg2++2(NO3)2-
-- What a nice watch! How long you it?
-- For just two weeks.
如图,CM,ON被AO所截,那么( )