Column I contains some cations and Column II contains some anions which produce a white precipitate with a corresponding cation. Match column I with Column II and select the correct code for your answer.

	Column I		Column II
P	${\text{Ag}}^{+}$	1	${\text{Cl}}^{-}$
Q	${\text{Zn}}^{2+}$	2	${\text{S}}^{2-}$
R	${\text{Mg}}^{2+}$	3	${\text{CO}}_3^{2-}$
S	${\text{Ba}}^{2+}$	4	${\text{SO}}_4^{2-}$