12. A gas turbine engine in which exhaust gas heat energy is added to the air charge between the compressor and combustion chamber is classified as which of the following?

A regenerative cycle engine utilizes a heat exchanger to transfer exhaust gas heat to the air charge before combustion, as described in the question. This process recovers waste heat, reducing fuel consumption, and distinguishes it from open, closed, or semi-open cycle engines, which do not incorporate this heat recovery mechanism.