Equivalent molar amounts of magnesium carbonate and strontium carbonate are heated separately so that complete thermal decomposition occurs. The lowest temperature at which this takes place is called $T_d$. After cooling, the residues are each added to the same volumes of water, and the pH change is recorded. This pH change is called $\Delta \text{pH}$. Which metal has the larger value of $T_d$, and the larger value of $\Delta \text{pH}$?
- A$T_d$: Mg, $\Delta \text{pH}$: Mg
- B$T_d$: Mg, $\Delta \text{pH}$: Sr
- C$T_d$: Sr, $\Delta \text{pH}$: Mg
- D$T_d$: Sr, $\Delta \text{pH}$: Sr