The correct option is C Magnesium Chloride, water and carbon dioxide
The reaction of any carbonates with HCl results in salt, hydrogen and evolution of some CO2 gas.
Here, magnesium carbonate reacts with HCl to give magnesium chloride(MgCl2. The overall reaction is as follows:
MgCO3 + HCl → MgCl2 + H2O + CO2