Here's a problem to solve: 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?

Among the 4 following options, which is the correct answer?

- A: the masses of compounds found in the engine
 
- B: the amount of heat in the engine
 
- C: the total mass of gasoline
 
- D: the total amount of energy
 