16. mgco₃(s) → mgo(s) + co₂(g)\nsynthesis\ncombustion\ndecomposition\nsingle replacement\ndouble replacement

Brief Explanations:

A decomposition reaction is one where a single compound breaks down into two or more simpler substances. In the given reaction, magnesium carbonate ($MgCO_3$) breaks down into magnesium oxide ($MgO$) and carbon - dioxide ($CO_2$). Synthesis is when two or more substances combine to form one compound. Combustion involves a reaction with oxygen and often produces heat and light. Single replacement is when one element replaces another in a compound, and double replacement is when the cations and anions of two different compounds exchange places.

Answer:

C. Decomposition