the masses of compounds found in the engine the amount of heat in the engine the total mass of gasoline the total amount of energy
I gave my students this multiple choice question: When a car engine is started, gasoline is mixed with air and burned. Heat, sound, and chemical products are released. As the engine operates, which of these remains constant?

Only one answer is correct among these 4 choices:
- the masses of compounds found in the engine
- the amount of heat in the engine
- the total mass of gasoline
- the total amount of energy

Could you tell me which one is correct?

the total amount of energy