Which of the following correctly gives the order of thermal stability of the group 2 carbonates together with the reason?

1. A$\mathrm{MgCO}{}_3<\mathrm{BaCO}{}_3<\mathrm{CaCO}{}_3$; stability depends only on the molar mass of the carbonate
2. Ball three have the same decomposition temperature because each contains $\mathrm{CO}{}_3{}^{2-}$
3. C$\mathrm{BaCO}{}_3<\mathrm{CaCO}{}_3<\mathrm{MgCO}{}_3$; the larger cation polarises the carbonate ion more
4. D$\mathrm{MgCO}{}_3<\mathrm{CaCO}{}_3<\mathrm{BaCO}{}_3$; the smaller cation polarises the carbonate ion more and favours formation of the oxide, which has a larger lattice enthalpy