High-Level Maintenance on Aircraft Is Performed by the Manufacturer

High-level maintenance on aircraft is performed by the manufacturer.  This service after the sale means that in the aircraft industry:

A) customers are relatively weak because of the high switching costs created by frequent-flyer programs.
B) the industry is moving toward differentiation of services.
C) the competitive rivalry in the industry is severe.
D) the economic segment of the external environment has shifted, but airline strategies have not changed.