When copper carbonate is heated it releases brisk effervescence given by gas? 

Effervescence is the process whereby a chemical reaction causes gas bubbles to develop in a liquid. We should be aware that when heated, copper carbonate splits into two different compounds before attempting to answer this issue.

We are aware that thermal decomposition is a chemical process in which the heating of a single material causes it to split into two or more simpler compounds. Since heat is necessary to break the substance's bonds, the reaction is often endothermic. Because of this, thermal energy must be continuously provided to the reaction to keep it continuing.
When heated, copper carbonate breaks down into copper oxide and carbon dioxide.
While copper oxide is dark, copper carbonate is green. During the response, we can notice a colour shift from green to black.

Decomposition reactions are defined as those reactions in which one compound is broken down to produce more substances.

An example of decomposition reaction is the decomposition of copper carbonate to form copper oxide and carbon dioxide.
${\mathrm{CuCO}}_3\to \mathrm{CuO}+{\mathrm{CO}}_2$

Hence option A is correct.