Firms such as BMW create a product mix with various product lines which are _____________________.

a. groups of associated items that consumers tend to use together or think of as part of a groups of similar products or services.

b. linked by supply chains and manufacturing similarities that will allow customers to easily interchange models from one category with another.

c. unsought product or services that consumers either do not normally think about buying or do not know about at all.

d. reflect marketing and logistical redundancies that can be expensive to design and maintain over decades of development.