Which use combustion to release thermal energy? furnaces and heat engines heat engines and heat pumps heat pumps and bimetallic coils bimetallic coils and furnaces

The correct answer is option A, Furnace and heat engines

Reason -

In furnace, material possessing chemical energy (that can be converted into heat energy through combustion) are burnt to generate some other form of energy. While in heat engine fuels such as petroleum products are burnt to produce energy to drive the vehicle or equipment.

While a heat pump is only responsible for heat transferring and thus there is no scope of combustion in it. While a bimetallic strip produces mechanical energy through the  change of temperature.  

the answer to your question is b