Which of the Following Would Be an Example of Partnering

Which of the following would be an example of partnering?

A) selling a customized bus to the CEO of the bus manufacturer
B) renting customized buses to corporate customers through a car service agency that services corporations
C) using the same brand of paint on all the buses they customize
D) developing a standardized process to ensure the buses all receive the same steps,with differences within those steps
E) creating two or more identical customizations for the same customer