Answer
a) $BaNO_3$
b) All three.
c) $KBr, Al_2Br_6$
Work Step by Step
a) $BaNO_3$
Sulfates are usually soluble but the barium one is an exception. Carbonates are usually insoluble and the barium one is not an exception. Nitrates are almost always soluble.
b) All three.
Salts of sodium are almost always soluble.
c) $KBr, Al_2Br_6$
Bromides are usually soluble, but the silver one is an exception.
