Answer:
.D.complementary products
Step-by-step explanation:
A complementary good is a product whose usage is dependent on the availability of another. Complementary goods are, therefore, goods that are used together. For example, A and B will be complimentary goods if the use of A will require the use of B.
Yachts and docks are complementary products because a yacht will require a dock as the base of its operation. Without a dock, yacht operations will be almost impossible. Bill is not making good sales on big yachts because potential customers cannot find sufficient docking space. Other examples of complementary goods are car and petrol, printers and ink cartridges, guns and bullets, and DVD players and DVD disks.