Answer
a. Insoluble.
b. Insoluble.
c. Insoluble.
d. Soluble.
Work Step by Step
a. When $Cl^-$, $Br^-$ or $I^-$ react with $Ag^+$, $Hg_2^{2+}$ or $Pb^{2+}$, the resulting ionic compound is insoluble.
b. Most of the time, compounds with $P{O_4}^{3-}$ are insoluble.
c. Most of the time, compounds with $C{O_3}^{2-}$ are insoluble.
d. Any common compound with $K^+$ is soluble.
