Correct answer:
C. veinte kilómetros por litro
Eficiencia de gasolina is defined as gas mileage. So this is defined as the distance a car can run per liter of petrol. The greater the distance the car run, the better the gas mileage. Therefore, from the options, we know that C. is the correct one. Therefore:
Francisco: Muy buena, mi auto anda veinte kilómetros por litro