Here's why:

* Combustion is a chemical process that involves the rapid reaction between a substance with an oxidant, usually oxygen, to produce heat and light.

* In your reaction, you have ethane (C2H6) reacting with oxygen (O2) to produce carbon dioxide (CO2) and water (H2O).

* The release of heat and light are characteristic of combustion reactions.

Therefore, the reaction 2C2H6 + 7O2g → 4CO2 + 6H2O is a combustion reaction.