Which of the Following Would Be Considered an Upstream Partner

Which of the following would be considered an upstream partner in a company's supply chain?

A) a firm that resells a finished product and shares the net sales with the producer
B) a firm that provides technical expertise in the production of a product
C) a firm that markets a product to consumers through social media
D) a firm that buys products at wholesale cost from the company
E) a firm that exclusively markets a product to other businesses