Answer
A
Work Step by Step
From Fig. 3-10
a) Soluble: $NO_3^-$
b) Insoluble: $S^{2-}$ and cation is not $NH_4^+$ or an alkali metal.
c) Insoluble: $PO_4^{3-}$ and cation is not $NH_4^+$ or an alkali metal.
d) Insoluble: $OH^-$ and cation is not an alkali metal, Ba or Sr.