Joe Girard's "Ferris Wheel" Concept Assumes Which of the Following

Joe Girard's "Ferris Wheel" concept assumes which of the following?

A) The optimal ratio of customers to prospects is 66 percent.
B) If the customers are sold the correct product and given good service, a company will not lose customers.
C) A certain number of customers will be lost every year by most companies.
D) Departing customers must be replaced by new customers at an equal rate.
E) Salespeople will do better prospecting when they think of the process as a roller coaster.