What should the CK administrator use to represent that Contact can be interested in multiple pieces of Merchandies?

CloudKicks (CK) stores information about specific customers in Contacts and information about shoes and accessories in a custom Merchandise object.

What should the CK administrator use to represent that Contact can be interested in multiple pieces of Merchandies?
A . Hierarchy column
B . Lookup filter
C . Formula field
D . Junction object

Answer: D