Which of the following metal carbonates decomposes on heating?

$BaSO_4 + C \rightarrow A + CO$
In the above reaction,$A$ is:

Identify the correct statement.

Which of the following magnetic properties is exhibited by the compounds of alkaline earth metals?

$A$ metal $M$ readily forms its sulphate $MSO_4$ which is water-soluble. It forms its oxide $MO$ which becomes inert on heating. It forms its insoluble hydroxide $M(OH)_2$ which is soluble in $NaOH$ solution. Then $M$ is

Which of the following represents the correct order of solubility in water?