Answer:
C.) leo washes all the cars and alex waxes all the cars
Step-by-step explanation:
If Leo and Alex share the job and decide that leo wash all the cars while Alex waxes all the cars, the service will be more efficient and faster.
That's because while Alex waxes a car that was washed by Leo, Leo is already washing another car and when that car is being waxed, Leo will already be washing another car. With this the service will be more dynamic, fast and efficient, because each worker will be using all his energy and concentration in a single service and will be able to pay more attention to every detail and make the service more uniform and well done.