Which of the Following Is Not a Good Example of a Substitute

Which of the following is not a good example of a substitute product that triggers stronger competitive pressures?

A) Artificial sweetener as a substitute for sugar
B) Wireless phone service as a substitute for a landline telephone
C) Coca-Cola as a substitute for Pepsi
D) Digital cameras as substitutes for film cameras
E) Video-on-demand services as a substitute for renting movies from a movie rental store