$A$ pair of substances which gives the same products on reaction with water is

Which of the following sulfates is insoluble in water?

$A$ chloride is significantly soluble in cold water. When placed on a $Pt$ wire and heated in a Bunsen flame,it does not impart any characteristic color to the flame. Which of the following cations is present?

The correct order of the solubility of sulphates of alkaline earth metals is:

Which alkaline earth metal chloride imparts an apple green color to the burner flame?

The compound $A$ on heating gives a colourless gas and a residue that is dissolved in water to obtain $B$. Excess of $CO_2$ is bubbled through aqueous solution of $B$,$C$ is formed which is recovered in the solid form. Solid $C$ on gentle heating gives back $A$. The compound $A$ is: