Answer
a) $CuCl_2$
b) $AgNO_3$
c) All three.
Work Step by Step
a) $CuCl_2$
Oxides and carbonates are insoluble and the cations in these two are not in the exception list. Chlorides are soluble and copper (||) is not in the exception list.
b) $AgNO_3$
Phosphates are insoluble and the silver is not in the exception list. Nitrates and iodates are soluble but silver is in the exception list for iodates.
c) All are soluble in water.
Salts of potassium are almost always soluble in water.
