PrimoDisk Inc. holds the highest market share in the low$-$growth compact disk industry. With the introduction of flash drives, the market for compact disks has reduced. However, PrimoDisk has been able to generate sufficient revenues for the parent company by selling its products in less developed countries. In the Boston Consulting Group $($BCG$)$ growth$-$share matrix, PrimoDisk will be categorized under

a$.$ dogs.

b$.$ cash cows.

c$.$ stars.

d$.$ question marks.