Answer:
Virtual retailer, is the right answer.
Step-by-step explanation:
A virtual retailer is a correct answer because the supply chain includes that manufacturer manufacture the product and then the whole seller sells the product to the retailer. Here the same trend can be seen that the McGraw-Hill publish a book so this company is a manufacturer and the last step from where the consumer to buy the commodity is the amazon. So amazon is classified as a virtual retailer.