For this case we can translate the sentence given as:
Emily: How is your car's gas efficiency?
Francisco: Very good, my car is going __________
The options are:
By definition, efficiency is about obtaining the greatest positive results with the minimum use of resources.
Then, if the efficiency of Francisco's car is very good, then the car is twenty miles traveled per liter of gasoline used.
Emily: How is your car's gas efficiency?
Francisco: Very good, my car is going Twenty km per liter
ANswer:
20 km por litro
Option C
